S. Spiller - Academia.edu (original) (raw)

Papers by S. Spiller

Origins of Life and Evolution of the Biosphere, 1986

The Journal of biological chemistry, Jan 5, 1988

We have isolated and determined the nucleotide and derived protein sequences for the four genes, ... more We have isolated and determined the nucleotide and derived protein sequences for the four genes, petCA and BD, which encode the cytochrome b6-f, electron-transfer complex of the filamentous cyanobacterium, Nostoc PCC 7906. The primary structure and cotranscription of the petCA genes encoding the Rieske-FeS (nuclear encoded in plants) and apocytochrome f proteins has been described previously (Kallas, T., Spiller, S., and Malkin, R. (1988) Proc. Natl. Acad. Sci. U.S.A., in press). The petBD genes (645 and 480 protein-coding nucleotides, respectively) for the apocytochrome b6 (24.3 kDa) and subunit-IV (17.5 kDa) proteins comprise a second operon located at least 12 kilobases (kb) from petCA. The Nostoc petBD genes are not closely linked to the psbB gene (encoding the 51-kDa photosystem II polypeptide) and do not contain introns as do the closely related chloroplast genes. DNA probes specific for each of the Nostoc cytochrome-complex genes hybridized to single bands in genomic DNA blot...

Proceedings of the National Academy of Sciences, 1988

The thylakoid membrane cytochrome b6-f complex (plastoquinol:oxidized-plastocyanin oxidoreductase... more The thylakoid membrane cytochrome b6-f complex (plastoquinol:oxidized-plastocyanin oxidoreductase, EC 1.10.99.1) catalyzes electron-transfer and proton-translocation reactions essential for oxygenic photosynthesis. We have isolated and determined the nucleotide sequences of the petC and petA genes encoding the Rieske Fe-S and cytochrome f polypeptides from the filamentous cyanobacterium Nostoc PCC 7906. These genes occur as single genomic copies, are tightly linked, and, as indicated by hybridization of genespecific probes to Nostoc RNA, are cotranscribed as a 2.0kilobase message. The Rieske Fe-S/cytochromefgene pair thus represents an example of clustering and cotranscription in cyanobacteria of functionally related genes that, in photosynthetic eukaryotes, reside on separate nuclear and plastid genomes. These data are consistent with the progressive degeneration of the modern chloroplast genomne from the ancestral, cyanobacterial-like genome ofan endosymbiont. The Rieske Fe-S and the mature cytochrome f apoproteins are encoded by 537 and 867 nucleotides and have molecular masses of 19.2 and 31.2 kDa, respectively. They show 59% and 60% protein sequence identity, respectively, relative to spinach. Forty-four amino acids (4.7 kDa) resembling a prokaryotic signal sequence precede apocytochrome f. In contrast, the Rieske Fe-S protein appears to be translated without a presequence. The 183 bases separating the Rieske Fe-S and preapocytochrome f genes contain two families of 7to 9-base tandem repeats, and some part of this sequence is highly reiterated in the genome. The C terminus of the Rieske Fe-S protein contains cysteine and histidine residues (probable ligands for the Fe2S2 center) in two peptides, Cys-Thr-His-Leu-Gly-Cys-Val and Cys-Pro-Cys-His-Gly-Ser, which have been conserved in spinach and in the five available Rieske Fe-S sequences from the mitochondrial-type cytochrome b-c1 complexes. Cytochrome f shows the heme binding residues Cys-Xaa-Xaa-Cys-His near its N terminus. Single, long hydrophobic stretches occur near the N and C termini, respectively, of the Rieske Fe-S and cytochrome f proteins and may form membrane-spanning helices. The thylakoid membranes ofplants, algae, and cyanobacteria house three intrinsic electron-transfer protein complexes essential to oxygenic photosynthesis. These are the photosystem (PS) II, the PS I, and the cytochrome b6-f (plastoquinol:oxidized-plastocyanin oxidoreductase, EC 1.10.99.1) complex. The latter catalyzes electron transfer from PS II to PS I, translocates protons across the membrane, and is required for both cyclic and noncyclic phosphorylation (1). Cytochrome b6-f complexes from plant (2) and cyanobacterial (3) sources contain two b-type hemes, one c-type heme (cytochrome I), a high-potential Fe2S2 center named after Rieske (4), and, as indicated by several lines of evidence

PLANT PHYSIOLOGY, 1987

Hydroponically grown pea seedlings (Pisum sativum L*, cv Alaska) were subjected to Fe stress for ... more Hydroponically grown pea seedlings (Pisum sativum L*, cv Alaska) were subjected to Fe stress for 10 to 16 days to produce mature chlorotic leaves. Greening was initiated by adding Fe to the nutrient solution. The levels of chlorophylls, chloroplast, and cytoplasmic rRNAs, and specific chloroplastand nucleus-encoded mRNAs were all significantly lower in leaves developing during iron stress than in nonstressed leaves. In plants greening after addition of Fe, nuclear transcripts encoding chlorophyll af b-binding protein and the small subunit of ribulose bisphosphate carboxylse/oxygenase increased about 5-fold in abundance following an 18 to 24 hour lag, as did the chloroplast-encoded transcript for the large subunit of the carboxylase/oxygenase. Chloroplast rRNA showed an increase over that in continually stressed control leaves only after a 40 hour lag. The chloroplast-encoded transcript encoding the QB-binding 32 kilodalton polypeptide of Photosystem II showed little change during greening. Chlorophyll itself increased gradually after a lag period of 24 hours, with an increase in chlorophyll a slightly preceding that of chlorophyll b. Kinetic considerations suggest that the changes observed represent a coordinate series of events initiated by readdition of Fe and occurring in parallel. Though accumulation of mRNA for light-harvesting, chlorophyll-a/b-binding protein might limit chlorophyll accumulation at the onset, subsequent changes in the mRNA do not parallel chlorophyll changes. All three of the mRNAs showing recovery on addition of Fe to Fe-stressed plants undergo sharp diurnal fluctuations in ab. Such fluctuations are comparable to those in nonstressed controls (mRNA for light-harvesting protein) or considerably more pronounced (mRNAs for carboxylase large and small subunits). The carboxylase small subunit mRNA and that for light-harvesting chlorophyll-binding protein were measured under constant conditions of light and temperature. Though a rhythm in greening leaves was hard to detect, it was prominent in the Fesufficient controls, persisting undamped through three full cycles for both mRNAs, and hence is probably circadian. 5 Abbreviations used: Cab RNA, RNA from the nuclear gene family coding for the Chl a/b protein of the light harvesting complex; psbA RNA, RNA from the chloroplast gene coding for the QB binding, 32,000 D photosystem II polypeptide; RbcS RNA, RNA from the nuclear gene family coding for the small subunit polypeptide of ribulose-bisphosphate carboxylase (RuP2,3-phospho-o-glycerate carboxylase [dimerizing],EC 41.1.39); rbcL RNA, RNA from the chloroplast gene coding for the large subunit of ribulose bisphosphate carboxylase; SSC, 0.15 M NaCl, 0.15 M Na citrate. 409

PLANT PHYSIOLOGY, 1980

It has been proposed that Fe stress may be used in the study of limiting factors in photosynthesi... more It has been proposed that Fe stress may be used in the study of limiting factors in photosynthesis as an expermental means of varying photochemical capacity in vivo (Plant Physiol 1980 65: 114-120). In this paper the effect of Fe stress on photosynthetic unit number, size, and composition was investigated by measuring P700, cytochrome (Cyt)f, chlorophyll (Chi) a, and Chi b in sugar beet leaves. The results show that when Fe stress reduced Chl per unit area by 80% (from 60 to 12 micrograms per square centimeter), it decreased the number of P700 molecules per unit area by 88% and Cyt f per unit area by 86%; over the same range the ChM to P700 ratio increased by 37% but there was no significant change in the Chi to Cyt f ratio. These data suggest that Fe stress decreases photochemical capacity and Chl per unit area by diminishing the number of photosynthetic units per unit leaf area.

PLANT PHYSIOLOGY, 1982

Corn (Zea mnays, L.), bean (Phaseolus vulgaris L.), barley (Hordeum vudgare L.), spinach (Spuiaci... more Corn (Zea mnays, L.), bean (Phaseolus vulgaris L.), barley (Hordeum vudgare L.), spinach (Spuiacia oeracea L.), and sugarbeet (Beta vulgaris L.) grown under iron deficiency, and Potamogeton pectinatus L, and Potamogeton nodosus Poir. grown under oxygen deficiency, contained less chlorophyll than the controls, but accumulated Mg-protoporphyrin IX and/ or Mg-protoporphyrin IX monomethyl ester. No significant accumulation of these intermediates was detected in the controls or in the tissue of plants stressed by S, Mg, N deficiency, or by prolonged dark treatment. Treatment of normal plant tissue with 8-aminolevulinic acid in the dark resulted in the accumulation of protochlorophyliide. If this treatment was carried out under conditions of iron or oxygen deficiency, less protochlorophyllide was formed, but a significant amount of Mg-protoporphyrin IX and Mg-protoporphyrin IX monomethyl ester accumulated. These results are consistent with the presence of an 02, Fe-requiring step between Mg-protoporphyrin IX monomethyl ester and protochlorophyllide. Iron and 02 are essential to a vast array of biological functions. In this investigation, we have attempted to study those effects that are directly related to the Chl biosynthetic pathway. In higher plants, Fe deficiency results in chlorosis. This relationship was carefully documented by DeKock et al. (6) and by Evans (8). Marsh et al. (15) noted an inhibition of '4C incorporation from citrate, succinate, and a-ketoglutarate into Chl in Fedeficient cowpeas. In photosynthetic bacteria, Fe deficiency results in the accumulation and excretion of intermediates in the tetrapyrrole biosynthetic pathway, particularly coproporphyrin (14). This finding led to the hypothesis that coproporphyrinogen oxidase (EC 1.3.3.3) is an Fe-requiring enzyme; and in fact the activity of the enzyme isolated from tobacco leaves was inhibited by chelating agents and stimulated by added Fe2+ (11). Recently, aquatic plants, notably rice and Echinochloa crusgalli (L.) Beauv., were shown to possess metabolic adaptations that allow them to germinate and grow under essentially complete anaerobiosis (20). The shoots produced under anaerobic conditions were chlorotic. Wang (22) reported that E. crusgalli germinated under anaerobic conditions produced shoots devoid of both Chl and Pchl(ide). The ultrastructure of the plastids was very abnormal (19). 02 is required in higher plant tissues for the accumulation of 'Supported by National Science Foundation Grant PCM 7813250.

Microscopy and Microanalysis, 2005

Biochemistry, 2008

Phytochromes are widely occurring red/far-red photoreceptors that utilize a linear tetrapyrrole (... more Phytochromes are widely occurring red/far-red photoreceptors that utilize a linear tetrapyrrole (bilin) chromophore covalently bound within a knotted PAS-GAF domain pair. Cyanobacteria also contain more distant relatives of phytochromes that lack this knot, such as the phytochrome-related cyanobacteriochromes implicated to function as blue/green switchable photoreceptors. In this study, we characterize the cyanobacteriochrome Tlr0924 from the thermophilic cyanobacterium Thermosynechococcus elongatus. Full-length Tlr0924 exhibits blue/green photoconversion across a broad range of temperatures, including physiologically relevant temperatures for this organism. Spectroscopic characterization of Tlr0924 demonstrates that its green-absorbing state is in equilibrium with a labile, spectrally distinct blue-absorbing species. The photochemically generated blue-absorbing state is in equilibrium with another species absorbing at longer wavelengths, giving a total of 4 states. Cys499 is essential for this behavior, because mutagenesis of this residue results in red-absorbing mutant biliproteins. Characterization of the C 499 D mutant protein by absorbance and CD spectroscopy supports the conclusion that its bilin chromophore adopts a similar conformation to the red-light-absorbing P r form of phytochrome. We propose a model photocycle in which Z/E photoisomerization of the 15/16 bond modulates formation of a reversible thioether linkage between Cys499 and C10 of the chromophore, providing the basis for the blue/green switching of cyanobacteriochromes.