Diego Gonzalez-halphen - Academia.edu (original) (raw)
Papers by Diego Gonzalez-halphen
Biochimica et Biophysica Acta (BBA) - Bioenergetics, 2016
Mitochondrial F1FO-ATP synthase of chlorophycean algae is isolated as a dimer. Besides the eight ... more Mitochondrial F1FO-ATP synthase of chlorophycean algae is isolated as a dimer. Besides the eight orthodox subunits (alpha, beta, gamma, delta, epsilon, OSCP, a and c), the enzyme contains nine atypical subunits (Asa1 to 9). These subunits build the peripheral stalk of the enzyme and stabilize its dimer structure. The location of the 60.6 kDa subunit Asa1 has been debated. On one hand, it was found in a transient subcomplex that contained membrane-bound subunits Asa1/Asa3/Asa5/Asa8/a (Atp6)/c (Atp8). On the other hand, Asa1 was proposed to form the bulky structure of the peripheral stalk that contacts the OSCP subunit in the F1 sector. Here, we over-expressed and purified the recombinant proteins Asa1 and OSCP and explored their interactions in vitro, using immunochemical techniques and affinity chromatography. Asa1 and OSCP interact strongly, and the carboxy-terminal half of OSCP seems to be instrumental for this association. In addition, the algal ATP synthase was partially dissociated at relatively high detergent concentrations, and an Asa1/Asa3/Asa5/Asa8/a/c10 subcomplex was characterized. Based on these results, a model is proposed in which Asa1 spans the whole peripheral arm of the enzyme, from a region close to the matrix-exposed side of the mitochondrial inner membrane to the F1 region where OSCP is located. We also suggest which residues in Asa1 and OSCP may mediate their interaction. Subunit b is the main component of the peripheral stalk of orthodox mitochondrial enzymes. Although no obvious sequence similarity exists between Asa1 and subunit b, both subunits probably play a similar structural role.
Science, 2007
Chlamydomonas reinhardtii is a unicellular green alga whose lineage diverged from land plants ove... more Chlamydomonas reinhardtii is a unicellular green alga whose lineage diverged from land plants over 1 billion years ago. It is a model system for studying chloroplast-based photosynthesis, as well as the structure, assembly, and function of eukaryotic flagella (cilia), which were inherited from the common ancestor of plants and animals, but lost in land plants. We sequenced the ∼120-megabase nuclear genome of Chlamydomonas and performed comparative phylogenomic analyses, identifying genes encoding uncharacterized proteins that are likely associated with the function and biogenesis of chloroplasts or eukaryotic flagella. Analyses of the Chlamydomonas genome advance our understanding of the ancestral eukaryotic cell, reveal previously unknown genes associated with photosynthetic and flagellar functions, and establish links between ciliopathy and the composition and function of flagella.
Biochimica et Biophysica Acta (BBA) - Bioenergetics, 2010
Biochimica et biophysica acta, Jul 1, 2017
Mitochondrial F1FO-ATP synthase of the chlorophycean algae Polytomella sp. can be isolated as a h... more Mitochondrial F1FO-ATP synthase of the chlorophycean algae Polytomella sp. can be isolated as a highly stable dimeric complex of 1600kDa. It is composed of eight highly conserved orthodox subunits (α, β, γ, δ, ε, OSCP, a, and c) and nine subunits (Asa1-9) that are exclusive of chlorophycean algae. The Asa subunits replace those that build up the peripheral stalk and the dimerization domains of the ATP synthase in other organisms. Little is known about the disposition of subunits Asa6, Asa8 and Asa9, that are predicted to have transmembrane stretches and that along with subunit a and a ring of c-subunits, seem to constitute the membrane-embedded Fo domain of the algal ATP synthase. Here, we over-expressed and purified the three Asa hydrophobic subunits and explored their interactions in vitro using a combination of immunochemical techniques, affinity chromatography, and an in vivo yeast-two hybrid assays. The results obtained suggest the following interactions Asa6-Asa6, Asa6-Asa8, A...
Biophysical Journal, 2017
Biological functions rely on ordered structures and intricately controlled collective dynamics. S... more Biological functions rely on ordered structures and intricately controlled collective dynamics. Such order in living systems is typically established and sustained by continuous dissipation of energy. The emergence of ordered patterns of motion is unique to non-equilibrium systems and is a manifestation of dynamic steady states. Many cellular processes require transitions between different steady states. Can general principles of statistical physics guide our understanding of such cellular self-organization? I will show that model actomyosin cortices, in the presence of rapid turnover, self-organize into three nonequilibrium steady states as a function of network connectivity. The different states arise from a subtle interaction between mechanical percolation of the actin network and myosin-generated stresses. All states show distinct dynamic order. Only the highest connectivity causes structural phase separation. We discover that the dominant mechanism defining the symmetries of the dynamic steady states is the emergence of ordered stress patterns. The marginally percolated state displays strong strain fluctuations, indicative of enhanced susceptibility. The striking dynamics in this model actomyosin cortex were revealed using fluorescent single-walled carbon nanotubes as novel probes. We propose self-organization of stress patterns as a new paradigm of biological function.
Biochimica et biophysica acta, Apr 12, 2017
Mitochondrial respiratory-chain complexes from Euglenozoa comprise classical subunits described i... more Mitochondrial respiratory-chain complexes from Euglenozoa comprise classical subunits described in other eukaryotes (i.e. mammals and fungi) and subunits that are restricted to Euglenozoa (e.g. Euglena gracilis and Trypanosoma brucei). Here we studied the mitochondrial F1FO-ATP synthase (or Complex V) from the photosynthetic eukaryote E. gracilis in detail. The enzyme was purified by a two-step chromatographic procedure and its subunit composition was resolved by a three-dimensional gel electrophoresis (BN/SDS/SDS). Twenty-two different subunits were identified by mass-spectrometry analyses among which the canonical α, β, γ, δ, ε, and OSCP subunits, and at least seven subunits previously found in Trypanosoma. The ADP/ATP carrier was also associated to the ATP synthase into a dimeric ATP synthasome. Single-particle analysis by transmission electron microscopy of the dimeric ATP synthase indicated that the structures of both the catalytic and central rotor parts are conserved while ot...
Mensaje Bioquimico, 2003
... En general las mitocondrias presentan una forma ovalada cuyo tamaño, estructura interna, y nú... more ... En general las mitocondrias presentan una forma ovalada cuyo tamaño, estructura interna, y número por célula varía en los diferentes tipos Flores Herrera O, Riveros Rosas H, Sosa Peinado A, Vázquez Contreras E (eds). Mensaje Bioquímico, Vol XXVII. ...
Biochimica et Biophysica Acta (BBA) - Bioenergetics, 2016
The algae Chlamydomonas reinhardtii and Polytomella sp., a green and a colorless member of the ch... more The algae Chlamydomonas reinhardtii and Polytomella sp., a green and a colorless member of the chlorophycean lineage respectively, exhibit a highly-stable dimeric mitochondrial F1Fo-ATP synthase (complex V), with a molecular mass of 1600kDa. Polytomella, lacking both chloroplasts and a cell wall, has greatly facilitated the purification of the algal ATP-synthase. Each monomer of the enzyme has 17 polypeptides, eight of which are the conserved, main functional components, and nine polypeptides (Asa1 to Asa9) unique to chlorophycean algae. These atypical subunits form the two robust peripheral stalks observed in the highly-stable dimer of the algal ATP synthase in several electron-microscopy studies. The topological disposition of the components of the enzyme has been addressed with cross-linking experiments in the isolated complex; generation of subcomplexes by limited dissociation of complex V; detection of subunit-subunit interactions using recombinant subunits; in vitro reconstitution of subcomplexes; silencing of the expression of Asa subunits; and modeling of the overall structural features of the complex by EM image reconstruction. Here, we report that the amphipathic polymer Amphipol A8-35 partially dissociates the enzyme, giving rise to two discrete dimeric subcomplexes, whose compositions were characterized. An updated model for the topological disposition of the 17 polypeptides that constitute the algal enzyme is suggested. This article is part of a Special Issue entitled 'EBEC 2016: 19th European Bioenergetics Conference, Riva del Garda, Italy, July 2-6, 2016', edited by Prof. Paolo Bernardi.
European Journal of Biochemistry
A defined medium with ethanol as sole carbon source was devised for growth of the colorless, unic... more A defined medium with ethanol as sole carbon source was devised for growth of the colorless, unicellular alga Polytomella spp. Cell density on this carbon source was related to extracellular pH. An acidic pH was required for ethanol utilization; best yields were obtained at pH 3.7. Spectroscopic analysis of the cells showed that the concentration of cytochrome c per cell was 40% higher than at pH 6.0; the concentrations of cytochrome a606 (cytochrome c oxidase) and b566 (cytochrome bc1 complex) were the same. A soluble cytochrome c550 was purified from cells grown at pH 3.7 and characterized by peptide sequencing as the 12-kDa cytochrome c550 of the mitochondrial respiratory chain. Immunoblots of total cell proteins showed higher accumulation of cytochrome c550 at pH 3.7 than at pH 6.0. RNA blot analysis gave clear evidence of the abundance of c550 transcript in cells grown at pH 3.7. The amount of mitochondrial proteins obtained from cells grown at pH 3.7 was twofold higher than th...
Cómo se perpetúa un error conceptual en la literatura científica Diego González-Halphen Universid... more Cómo se perpetúa un error conceptual en la literatura científica Diego González-Halphen Universidad Nacional Autónoma de México Uno de los términos más maltratados en la literatura científica biológica es la palabra «homología», cuya utilización errónea está ampliamente extendida. Con frecuencia encontramos frases que contienen los términos «porcentaje de homología» o «altamente homólogo», o bien «baja homología», que parecen otorgar a la palabra «homología» un valor cuantitativo, al que puede asignársele un valor numérico. El término «homología» tiene un significado científico muy claro: define un origen evolutivo común para las estructuras biológicas. No es un término cuantitativo, es un término cualitativo que denota «todo o nada». Un ejemplo clásico de la utilización del término se da en la comparación de las alas de los murciélagos, las aletas de los manatíes y las patas de un topo. 1 Evidentemente, estas estructuras tienen funciones muy diferentes: alas para volar, aletas para nadar y patas para escarbar; sin embargo, todas comparten características que delatan un origen común para los tres mamíferos: las tres tienen huesos largos equivalentes a brazos, los huesos equivalentes a las muñecas son pequeños y todas tienen cinco dígitos. Por lo tanto, se trata de estructuras homólogas, ya que tienen un origen evolutivo común. Los tres mamíferos del ejemplo comparten el mismo ancestro en su historia evolutiva, por lo que las estructuras óseas correspondientes (independientemente de que lleven a cabo o no una función similar) tienen el mismo origen. En contraste, el término «analogía» se usa para describir estructuras que llevan a cabo funciones semejantes pero cuyo origen evolutivo es completamente distinto: tal es el caso de las alas de los pájaros, las alas de los murciélagos y las alas de los mosquitos. Todas son indispensables para el vuelo, pero los organismos que las tienen no comparten un ancestro común. Los orígenes de estas estructuras tienen historias evolutivas completamente distintas.
La revista Ludus Vitalis le presenta un reto formidable a los científicos con su pregunta, ¿De qu... more La revista Ludus Vitalis le presenta un reto formidable a los científicos con su pregunta, ¿De qué forma, el desarrollo de conocimientos científicos de su disciplina ha modificado las posibilidades de acción humana? Una respuesta inmediata y sincera es: de ninguna. ¿Me preocupa dar esta respuesta? No, no me preocupa. No me preocupa, como tampoco me preocupa que una orquesta sinfónica no tenga un impacto "productivo" en nuestra sociedad. No produce un bien económico, no es una empresa que genera empleos y, sin embargo, es una parte indispensable de nuestra sociedad.
Archives of biochemistry and biophysics, Jan 2, 2015
The F1FO-ATP synthase of the colorless alga Polytomella sp. exhibits a robust peripheral arm cons... more The F1FO-ATP synthase of the colorless alga Polytomella sp. exhibits a robust peripheral arm constituted by nine atypical subunits only present in chlorophycean algae. The isolated dimeric enzyme exhibits a latent ATP hydrolytic activity which can be activated by some detergents. To date, the kinetic behavior of the algal ATPase has not been studied. Here we show that while the soluble F1 sector exhibits Michaelis-Menten kinetics, the dimer exhibits a more complex behavior. The kinetic parameters (Vmax and Km) were obtained for both the F1 sector and the dimeric enzyme as isolated or activated by detergent, and this activation was also seen on the enzyme reconstituted in liposomes. Unlike other ATP synthases, the algal dimer hydrolyzes ATP on a wide range of pH and temperature. The enzyme was inhibited by oligomycin, DCCD and Mg-ADP, although oligomycin induced a peculiar inhibition pattern that can be attributed to structural differences in the algal subunit-c. The hydrolytic activ...
Journal of bacteriology, 1995
Purification of the glutamate synthase (GOGAT) enzyme from Saccharomyces cerevisiae showed that i... more Purification of the glutamate synthase (GOGAT) enzyme from Saccharomyces cerevisiae showed that it is an oligomeric enzyme composed of three identical 199-kDa subunits. The GOGAT structural gene was isolated by screening a yeast genomic library with a yeast PCR probe. This probe was obtained by amplification with degenerate oligonucleotides designed from conserved regions of known GOGAT genes. The derived amino-terminal sequence of the GOGAT gene was confirmed by direct amino-terminal sequence analysis of the purified protein of 199 kDa. Northern (RNA) analysis allowed the identification of an mRNA of about 7 or 8 kb. An internal fragment of the GOGAT gene was used to obtain null GOGAT mutants completely devoid of GOGAT activity. The results show that S. cerevisiae has a single NADH-GOGAT enzyme, consisting of three 199-kDa monomers, that differs from the one found in prokaryotic microorganisms but is similar to those found in other eukaryotic organisms such as alfalfa.
Biochimica et Biophysica Acta (BBA) - Bioenergetics, 2014
Cell Death and Disease, 2011
Mitochondrial dysfunction often leads to cell death and disease. We can now draw correlations bet... more Mitochondrial dysfunction often leads to cell death and disease. We can now draw correlations between the dysfunction of one of the most important mitochondrial enzymes, NADH:ubiquinone reductase or complex I, and its structural organization thanks to the recent advances in the X-ray structure of its bacterial homologs. The new structural information on bacterial complex I provide essential clues to finally understand how complex I may work. However, the same information remains difficult to interpret for many scientists working on mitochondrial complex I from different angles, especially in the field of cell death. Here, we present a novel way of interpreting the bacterial structural information in accessible terms. On the basis of the analogy to semi-automatic shotguns, we propose a novel functional model that incorporates recent structural information with previous evidence derived from studies on mitochondrial diseases, as well as functional bioenergetics.
Current Topics in Bioenergetics, 1987
The algae of the family Chlamydomonadaceae lack the gene cox3 that encodes subunit III of cytochr... more The algae of the family Chlamydomonadaceae lack the gene cox3 that encodes subunit III of cytochrome c oxi- dase in their mitochondrial genomes. This observation has raised the question of whether this subunit is pres- ent in cytochrome c oxidase or whether the correspond- ing gene is located in the nucleus. Cytochrome c oxidase was isolated from the colorless chlamydomonad
Biochimica et Biophysica Acta (BBA) - Bioenergetics, 2016
Mitochondrial F1FO-ATP synthase of chlorophycean algae is isolated as a dimer. Besides the eight ... more Mitochondrial F1FO-ATP synthase of chlorophycean algae is isolated as a dimer. Besides the eight orthodox subunits (alpha, beta, gamma, delta, epsilon, OSCP, a and c), the enzyme contains nine atypical subunits (Asa1 to 9). These subunits build the peripheral stalk of the enzyme and stabilize its dimer structure. The location of the 60.6 kDa subunit Asa1 has been debated. On one hand, it was found in a transient subcomplex that contained membrane-bound subunits Asa1/Asa3/Asa5/Asa8/a (Atp6)/c (Atp8). On the other hand, Asa1 was proposed to form the bulky structure of the peripheral stalk that contacts the OSCP subunit in the F1 sector. Here, we over-expressed and purified the recombinant proteins Asa1 and OSCP and explored their interactions in vitro, using immunochemical techniques and affinity chromatography. Asa1 and OSCP interact strongly, and the carboxy-terminal half of OSCP seems to be instrumental for this association. In addition, the algal ATP synthase was partially dissociated at relatively high detergent concentrations, and an Asa1/Asa3/Asa5/Asa8/a/c10 subcomplex was characterized. Based on these results, a model is proposed in which Asa1 spans the whole peripheral arm of the enzyme, from a region close to the matrix-exposed side of the mitochondrial inner membrane to the F1 region where OSCP is located. We also suggest which residues in Asa1 and OSCP may mediate their interaction. Subunit b is the main component of the peripheral stalk of orthodox mitochondrial enzymes. Although no obvious sequence similarity exists between Asa1 and subunit b, both subunits probably play a similar structural role.
Science, 2007
Chlamydomonas reinhardtii is a unicellular green alga whose lineage diverged from land plants ove... more Chlamydomonas reinhardtii is a unicellular green alga whose lineage diverged from land plants over 1 billion years ago. It is a model system for studying chloroplast-based photosynthesis, as well as the structure, assembly, and function of eukaryotic flagella (cilia), which were inherited from the common ancestor of plants and animals, but lost in land plants. We sequenced the ∼120-megabase nuclear genome of Chlamydomonas and performed comparative phylogenomic analyses, identifying genes encoding uncharacterized proteins that are likely associated with the function and biogenesis of chloroplasts or eukaryotic flagella. Analyses of the Chlamydomonas genome advance our understanding of the ancestral eukaryotic cell, reveal previously unknown genes associated with photosynthetic and flagellar functions, and establish links between ciliopathy and the composition and function of flagella.
Biochimica et Biophysica Acta (BBA) - Bioenergetics, 2010
Biochimica et biophysica acta, Jul 1, 2017
Mitochondrial F1FO-ATP synthase of the chlorophycean algae Polytomella sp. can be isolated as a h... more Mitochondrial F1FO-ATP synthase of the chlorophycean algae Polytomella sp. can be isolated as a highly stable dimeric complex of 1600kDa. It is composed of eight highly conserved orthodox subunits (α, β, γ, δ, ε, OSCP, a, and c) and nine subunits (Asa1-9) that are exclusive of chlorophycean algae. The Asa subunits replace those that build up the peripheral stalk and the dimerization domains of the ATP synthase in other organisms. Little is known about the disposition of subunits Asa6, Asa8 and Asa9, that are predicted to have transmembrane stretches and that along with subunit a and a ring of c-subunits, seem to constitute the membrane-embedded Fo domain of the algal ATP synthase. Here, we over-expressed and purified the three Asa hydrophobic subunits and explored their interactions in vitro using a combination of immunochemical techniques, affinity chromatography, and an in vivo yeast-two hybrid assays. The results obtained suggest the following interactions Asa6-Asa6, Asa6-Asa8, A...
Biophysical Journal, 2017
Biological functions rely on ordered structures and intricately controlled collective dynamics. S... more Biological functions rely on ordered structures and intricately controlled collective dynamics. Such order in living systems is typically established and sustained by continuous dissipation of energy. The emergence of ordered patterns of motion is unique to non-equilibrium systems and is a manifestation of dynamic steady states. Many cellular processes require transitions between different steady states. Can general principles of statistical physics guide our understanding of such cellular self-organization? I will show that model actomyosin cortices, in the presence of rapid turnover, self-organize into three nonequilibrium steady states as a function of network connectivity. The different states arise from a subtle interaction between mechanical percolation of the actin network and myosin-generated stresses. All states show distinct dynamic order. Only the highest connectivity causes structural phase separation. We discover that the dominant mechanism defining the symmetries of the dynamic steady states is the emergence of ordered stress patterns. The marginally percolated state displays strong strain fluctuations, indicative of enhanced susceptibility. The striking dynamics in this model actomyosin cortex were revealed using fluorescent single-walled carbon nanotubes as novel probes. We propose self-organization of stress patterns as a new paradigm of biological function.
Biochimica et biophysica acta, Apr 12, 2017
Mitochondrial respiratory-chain complexes from Euglenozoa comprise classical subunits described i... more Mitochondrial respiratory-chain complexes from Euglenozoa comprise classical subunits described in other eukaryotes (i.e. mammals and fungi) and subunits that are restricted to Euglenozoa (e.g. Euglena gracilis and Trypanosoma brucei). Here we studied the mitochondrial F1FO-ATP synthase (or Complex V) from the photosynthetic eukaryote E. gracilis in detail. The enzyme was purified by a two-step chromatographic procedure and its subunit composition was resolved by a three-dimensional gel electrophoresis (BN/SDS/SDS). Twenty-two different subunits were identified by mass-spectrometry analyses among which the canonical α, β, γ, δ, ε, and OSCP subunits, and at least seven subunits previously found in Trypanosoma. The ADP/ATP carrier was also associated to the ATP synthase into a dimeric ATP synthasome. Single-particle analysis by transmission electron microscopy of the dimeric ATP synthase indicated that the structures of both the catalytic and central rotor parts are conserved while ot...
Mensaje Bioquimico, 2003
... En general las mitocondrias presentan una forma ovalada cuyo tamaño, estructura interna, y nú... more ... En general las mitocondrias presentan una forma ovalada cuyo tamaño, estructura interna, y número por célula varía en los diferentes tipos Flores Herrera O, Riveros Rosas H, Sosa Peinado A, Vázquez Contreras E (eds). Mensaje Bioquímico, Vol XXVII. ...
Biochimica et Biophysica Acta (BBA) - Bioenergetics, 2016
The algae Chlamydomonas reinhardtii and Polytomella sp., a green and a colorless member of the ch... more The algae Chlamydomonas reinhardtii and Polytomella sp., a green and a colorless member of the chlorophycean lineage respectively, exhibit a highly-stable dimeric mitochondrial F1Fo-ATP synthase (complex V), with a molecular mass of 1600kDa. Polytomella, lacking both chloroplasts and a cell wall, has greatly facilitated the purification of the algal ATP-synthase. Each monomer of the enzyme has 17 polypeptides, eight of which are the conserved, main functional components, and nine polypeptides (Asa1 to Asa9) unique to chlorophycean algae. These atypical subunits form the two robust peripheral stalks observed in the highly-stable dimer of the algal ATP synthase in several electron-microscopy studies. The topological disposition of the components of the enzyme has been addressed with cross-linking experiments in the isolated complex; generation of subcomplexes by limited dissociation of complex V; detection of subunit-subunit interactions using recombinant subunits; in vitro reconstitution of subcomplexes; silencing of the expression of Asa subunits; and modeling of the overall structural features of the complex by EM image reconstruction. Here, we report that the amphipathic polymer Amphipol A8-35 partially dissociates the enzyme, giving rise to two discrete dimeric subcomplexes, whose compositions were characterized. An updated model for the topological disposition of the 17 polypeptides that constitute the algal enzyme is suggested. This article is part of a Special Issue entitled 'EBEC 2016: 19th European Bioenergetics Conference, Riva del Garda, Italy, July 2-6, 2016', edited by Prof. Paolo Bernardi.
European Journal of Biochemistry
A defined medium with ethanol as sole carbon source was devised for growth of the colorless, unic... more A defined medium with ethanol as sole carbon source was devised for growth of the colorless, unicellular alga Polytomella spp. Cell density on this carbon source was related to extracellular pH. An acidic pH was required for ethanol utilization; best yields were obtained at pH 3.7. Spectroscopic analysis of the cells showed that the concentration of cytochrome c per cell was 40% higher than at pH 6.0; the concentrations of cytochrome a606 (cytochrome c oxidase) and b566 (cytochrome bc1 complex) were the same. A soluble cytochrome c550 was purified from cells grown at pH 3.7 and characterized by peptide sequencing as the 12-kDa cytochrome c550 of the mitochondrial respiratory chain. Immunoblots of total cell proteins showed higher accumulation of cytochrome c550 at pH 3.7 than at pH 6.0. RNA blot analysis gave clear evidence of the abundance of c550 transcript in cells grown at pH 3.7. The amount of mitochondrial proteins obtained from cells grown at pH 3.7 was twofold higher than th...
Cómo se perpetúa un error conceptual en la literatura científica Diego González-Halphen Universid... more Cómo se perpetúa un error conceptual en la literatura científica Diego González-Halphen Universidad Nacional Autónoma de México Uno de los términos más maltratados en la literatura científica biológica es la palabra «homología», cuya utilización errónea está ampliamente extendida. Con frecuencia encontramos frases que contienen los términos «porcentaje de homología» o «altamente homólogo», o bien «baja homología», que parecen otorgar a la palabra «homología» un valor cuantitativo, al que puede asignársele un valor numérico. El término «homología» tiene un significado científico muy claro: define un origen evolutivo común para las estructuras biológicas. No es un término cuantitativo, es un término cualitativo que denota «todo o nada». Un ejemplo clásico de la utilización del término se da en la comparación de las alas de los murciélagos, las aletas de los manatíes y las patas de un topo. 1 Evidentemente, estas estructuras tienen funciones muy diferentes: alas para volar, aletas para nadar y patas para escarbar; sin embargo, todas comparten características que delatan un origen común para los tres mamíferos: las tres tienen huesos largos equivalentes a brazos, los huesos equivalentes a las muñecas son pequeños y todas tienen cinco dígitos. Por lo tanto, se trata de estructuras homólogas, ya que tienen un origen evolutivo común. Los tres mamíferos del ejemplo comparten el mismo ancestro en su historia evolutiva, por lo que las estructuras óseas correspondientes (independientemente de que lleven a cabo o no una función similar) tienen el mismo origen. En contraste, el término «analogía» se usa para describir estructuras que llevan a cabo funciones semejantes pero cuyo origen evolutivo es completamente distinto: tal es el caso de las alas de los pájaros, las alas de los murciélagos y las alas de los mosquitos. Todas son indispensables para el vuelo, pero los organismos que las tienen no comparten un ancestro común. Los orígenes de estas estructuras tienen historias evolutivas completamente distintas.
La revista Ludus Vitalis le presenta un reto formidable a los científicos con su pregunta, ¿De qu... more La revista Ludus Vitalis le presenta un reto formidable a los científicos con su pregunta, ¿De qué forma, el desarrollo de conocimientos científicos de su disciplina ha modificado las posibilidades de acción humana? Una respuesta inmediata y sincera es: de ninguna. ¿Me preocupa dar esta respuesta? No, no me preocupa. No me preocupa, como tampoco me preocupa que una orquesta sinfónica no tenga un impacto "productivo" en nuestra sociedad. No produce un bien económico, no es una empresa que genera empleos y, sin embargo, es una parte indispensable de nuestra sociedad.
Archives of biochemistry and biophysics, Jan 2, 2015
The F1FO-ATP synthase of the colorless alga Polytomella sp. exhibits a robust peripheral arm cons... more The F1FO-ATP synthase of the colorless alga Polytomella sp. exhibits a robust peripheral arm constituted by nine atypical subunits only present in chlorophycean algae. The isolated dimeric enzyme exhibits a latent ATP hydrolytic activity which can be activated by some detergents. To date, the kinetic behavior of the algal ATPase has not been studied. Here we show that while the soluble F1 sector exhibits Michaelis-Menten kinetics, the dimer exhibits a more complex behavior. The kinetic parameters (Vmax and Km) were obtained for both the F1 sector and the dimeric enzyme as isolated or activated by detergent, and this activation was also seen on the enzyme reconstituted in liposomes. Unlike other ATP synthases, the algal dimer hydrolyzes ATP on a wide range of pH and temperature. The enzyme was inhibited by oligomycin, DCCD and Mg-ADP, although oligomycin induced a peculiar inhibition pattern that can be attributed to structural differences in the algal subunit-c. The hydrolytic activ...
Journal of bacteriology, 1995
Purification of the glutamate synthase (GOGAT) enzyme from Saccharomyces cerevisiae showed that i... more Purification of the glutamate synthase (GOGAT) enzyme from Saccharomyces cerevisiae showed that it is an oligomeric enzyme composed of three identical 199-kDa subunits. The GOGAT structural gene was isolated by screening a yeast genomic library with a yeast PCR probe. This probe was obtained by amplification with degenerate oligonucleotides designed from conserved regions of known GOGAT genes. The derived amino-terminal sequence of the GOGAT gene was confirmed by direct amino-terminal sequence analysis of the purified protein of 199 kDa. Northern (RNA) analysis allowed the identification of an mRNA of about 7 or 8 kb. An internal fragment of the GOGAT gene was used to obtain null GOGAT mutants completely devoid of GOGAT activity. The results show that S. cerevisiae has a single NADH-GOGAT enzyme, consisting of three 199-kDa monomers, that differs from the one found in prokaryotic microorganisms but is similar to those found in other eukaryotic organisms such as alfalfa.
Biochimica et Biophysica Acta (BBA) - Bioenergetics, 2014
Cell Death and Disease, 2011
Mitochondrial dysfunction often leads to cell death and disease. We can now draw correlations bet... more Mitochondrial dysfunction often leads to cell death and disease. We can now draw correlations between the dysfunction of one of the most important mitochondrial enzymes, NADH:ubiquinone reductase or complex I, and its structural organization thanks to the recent advances in the X-ray structure of its bacterial homologs. The new structural information on bacterial complex I provide essential clues to finally understand how complex I may work. However, the same information remains difficult to interpret for many scientists working on mitochondrial complex I from different angles, especially in the field of cell death. Here, we present a novel way of interpreting the bacterial structural information in accessible terms. On the basis of the analogy to semi-automatic shotguns, we propose a novel functional model that incorporates recent structural information with previous evidence derived from studies on mitochondrial diseases, as well as functional bioenergetics.
Current Topics in Bioenergetics, 1987
The algae of the family Chlamydomonadaceae lack the gene cox3 that encodes subunit III of cytochr... more The algae of the family Chlamydomonadaceae lack the gene cox3 that encodes subunit III of cytochrome c oxi- dase in their mitochondrial genomes. This observation has raised the question of whether this subunit is pres- ent in cytochrome c oxidase or whether the correspond- ing gene is located in the nucleus. Cytochrome c oxidase was isolated from the colorless chlamydomonad