Eileen Jaffe - Academia.edu (original) (raw)
Papers by Eileen Jaffe
Apicomplexan parasites (including Plasmodium spp. and Toxoplasma gondii) employ a four-carbon pat... more Apicomplexan parasites (including Plasmodium spp. and Toxoplasma gondii) employ a four-carbon pathway for de novo heme biosynthesis, but this pathway is distinct from the animal/ fungal C4 pathway in that it is distributed between three compartments: the mitochondrion, cytosol, and apicoplast, a plastid acquired by secondary endosymbiosis of an alga. Parasite porphobilinogen synthase (PBGS) resides within the apicoplast, and phylogenetic analysis indicates a plant origin. The PBGS family exhibits a complex use of metal ions (Zn 2؉ and Mg 2؉) and oligomeric states (dimers, hexamers, and octamers). Recombinant T. gondii PBGS (TgPBGS) was purified as a stable ϳ320-kDa octamer, and low levels of dimers but no hexamers were also observed. The enzyme displays a broad activity peak (pH 7-8.5), with a K m for aminolevulinic acid of ϳ150 M and specific activity of ϳ24 mol of porphobilinogen/mg of protein/h. Like the plant enzyme, TgPBGS responds to Mg 2؉ but not Zn 2؉ and shows two Mg 2؉ affinities, interpreted as tight binding at both the active and allosteric sites. Unlike other Mg 2؉-binding PBGS, however, metal ions are not required for TgPBGS octamer stability. A mutant enzyme lacking the C-terminal 13 amino acids distinguishing parasite PBGS from plant and animal enzymes purified as a dimer, suggesting that the C terminus is required for octamer stability. Parasite heme biosynthesis is inhibited (and parasites are killed) by succinylacetone, an active site-directed suicide substrate. The distinct phylogenetic, enzymatic, and structural features of apicomplexan PBGS offer scope for developing selective inhibitors of the parasite enzyme based on its quaternary structure characteristics.
Apicomplexan parasites (including Plasmodium spp. and Toxoplasma gondii) employ a four-carbon pat... more Apicomplexan parasites (including Plasmodium spp. and Toxoplasma gondii) employ a four-carbon pathway for de novo heme biosynthesis, but this pathway is distinct from the animal/ fungal C4 pathway in that it is distributed between three compartments: the mitochondrion, cytosol, and apicoplast, a plastid acquired by secondary endosymbiosis of an alga. Parasite porphobilinogen synthase (PBGS) resides within the apicoplast, and phylogenetic analysis indicates a plant origin. The PBGS family exhibits a complex use of metal ions (Zn 2؉ and Mg 2؉) and oligomeric states (dimers, hexamers, and octamers). Recombinant T. gondii PBGS (TgPBGS) was purified as a stable ϳ320-kDa octamer, and low levels of dimers but no hexamers were also observed. The enzyme displays a broad activity peak (pH 7-8.5), with a K m for aminolevulinic acid of ϳ150 M and specific activity of ϳ24 mol of porphobilinogen/mg of protein/h. Like the plant enzyme, TgPBGS responds to Mg 2؉ but not Zn 2؉ and shows two Mg 2؉ affinities, interpreted as tight binding at both the active and allosteric sites. Unlike other Mg 2؉-binding PBGS, however, metal ions are not required for TgPBGS octamer stability. A mutant enzyme lacking the C-terminal 13 amino acids distinguishing parasite PBGS from plant and animal enzymes purified as a dimer, suggesting that the C terminus is required for octamer stability. Parasite heme biosynthesis is inhibited (and parasites are killed) by succinylacetone, an active site-directed suicide substrate. The distinct phylogenetic, enzymatic, and structural features of apicomplexan PBGS offer scope for developing selective inhibitors of the parasite enzyme based on its quaternary structure characteristics.
Small molecule docking to protein targets was developed as a drug discovery tool at a time when d... more Small molecule docking to protein targets was developed as a drug discovery tool at a time when drug discovery was focused predominantly on enzyme active sites rather than allosteric sites. However, as early as 1963, Monod and coworkers astutely pointed out that protein function can be regulated allosterically by small molecules that need not be structurally related to a protein's target (e.g. substrate) because they bind somewhere other than the active site . Some allosteric sites are similar to active sites, which are often located in deep grooves, somewhat buried in the protein structure, and contain a limited set of residues that provide a well defined binding site. Other allosteric sites are more like protein-protein interfaces (PPIs), which have less rigid binding requirements, frequently have species-specific variations in composition, and have overall greater structural flexibility.
BMC cancer, Jan 28, 2015
Overexpression or mutation of the epidermal growth factor receptor (EGFR) potently enhances the g... more Overexpression or mutation of the epidermal growth factor receptor (EGFR) potently enhances the growth of many solid tumors. Tumor cells frequently display resistance to mechanistically-distinct EGFR-directed therapeutic agents, making it valuable to develop therapeutics that work by additional mechanisms. Current EGFR-targeting therapeutics include antibodies targeting the extracellular domains, and small molecules inhibiting the intracellular kinase domain. Recent studies have identified a novel prone extracellular tetrameric EGFR configuration, which we identify as a potential target for drug discovery. Our focus is on the prone EGFR tetramer, which contains a novel protein-protein interface involving extracellular domain III. This EGFR tetramer is computationally targeted for stabilization by small molecule ligand binding. This study performed virtual screening of a Life Chemicals, Inc. small molecule library of 345,232 drug-like compounds against a molecular dynamics simulation...
![Research paper thumbnail of 5-Chloro[1,4-13C]levulinic acid modification of mammalian and bacterial porphobilinogen synthase suggests an active site containing two Zn(II)](https://a.academia-assets.com/images/blank-paper.jpg)
](Biochemistry, 1994
Page 1. 11554 Biochemistry 1994, 33, 1 1554-1 1562 5-Chloro[ 1 ,4-13C]le~~linic Acid Modification... more Page 1. 11554 Biochemistry 1994, 33, 1 1554-1 1562 5-Chloro[ 1 ,4-13C]le~~linic Acid Modification of Mammalian and Bacterial Porphobilinogen Synthase Suggests an Active Site Containing Two Zn( II)+ Eileen K. Jaffe,' Marina ...
Apicomplexan parasites (including Plasmodium spp. and Toxoplasma gondii) employ a four-carbon pat... more Apicomplexan parasites (including Plasmodium spp. and Toxoplasma gondii) employ a four-carbon pathway for de novo heme biosynthesis, but this pathway is distinct from the animal/ fungal C4 pathway in that it is distributed between three compartments: the mitochondrion, cytosol, and apicoplast, a plastid acquired by secondary endosymbiosis of an alga. Parasite porphobilinogen synthase (PBGS) resides within the apicoplast, and phylogenetic analysis indicates a plant origin. The PBGS family exhibits a complex use of metal ions (Zn 2؉ and Mg 2؉) and oligomeric states (dimers, hexamers, and octamers). Recombinant T. gondii PBGS (TgPBGS) was purified as a stable ϳ320-kDa octamer, and low levels of dimers but no hexamers were also observed. The enzyme displays a broad activity peak (pH 7-8.5), with a K m for aminolevulinic acid of ϳ150 M and specific activity of ϳ24 mol of porphobilinogen/mg of protein/h. Like the plant enzyme, TgPBGS responds to Mg 2؉ but not Zn 2؉ and shows two Mg 2؉ affinities, interpreted as tight binding at both the active and allosteric sites. Unlike other Mg 2؉-binding PBGS, however, metal ions are not required for TgPBGS octamer stability. A mutant enzyme lacking the C-terminal 13 amino acids distinguishing parasite PBGS from plant and animal enzymes purified as a dimer, suggesting that the C terminus is required for octamer stability. Parasite heme biosynthesis is inhibited (and parasites are killed) by succinylacetone, an active site-directed suicide substrate. The distinct phylogenetic, enzymatic, and structural features of apicomplexan PBGS offer scope for developing selective inhibitors of the parasite enzyme based on its quaternary structure characteristics.
Apicomplexan parasites (including Plasmodium spp. and Toxoplasma gondii) employ a four-carbon pat... more Apicomplexan parasites (including Plasmodium spp. and Toxoplasma gondii) employ a four-carbon pathway for de novo heme biosynthesis, but this pathway is distinct from the animal/ fungal C4 pathway in that it is distributed between three compartments: the mitochondrion, cytosol, and apicoplast, a plastid acquired by secondary endosymbiosis of an alga. Parasite porphobilinogen synthase (PBGS) resides within the apicoplast, and phylogenetic analysis indicates a plant origin. The PBGS family exhibits a complex use of metal ions (Zn 2؉ and Mg 2؉) and oligomeric states (dimers, hexamers, and octamers). Recombinant T. gondii PBGS (TgPBGS) was purified as a stable ϳ320-kDa octamer, and low levels of dimers but no hexamers were also observed. The enzyme displays a broad activity peak (pH 7-8.5), with a K m for aminolevulinic acid of ϳ150 M and specific activity of ϳ24 mol of porphobilinogen/mg of protein/h. Like the plant enzyme, TgPBGS responds to Mg 2؉ but not Zn 2؉ and shows two Mg 2؉ affinities, interpreted as tight binding at both the active and allosteric sites. Unlike other Mg 2؉-binding PBGS, however, metal ions are not required for TgPBGS octamer stability. A mutant enzyme lacking the C-terminal 13 amino acids distinguishing parasite PBGS from plant and animal enzymes purified as a dimer, suggesting that the C terminus is required for octamer stability. Parasite heme biosynthesis is inhibited (and parasites are killed) by succinylacetone, an active site-directed suicide substrate. The distinct phylogenetic, enzymatic, and structural features of apicomplexan PBGS offer scope for developing selective inhibitors of the parasite enzyme based on its quaternary structure characteristics.
Small molecule docking to protein targets was developed as a drug discovery tool at a time when d... more Small molecule docking to protein targets was developed as a drug discovery tool at a time when drug discovery was focused predominantly on enzyme active sites rather than allosteric sites. However, as early as 1963, Monod and coworkers astutely pointed out that protein function can be regulated allosterically by small molecules that need not be structurally related to a protein's target (e.g. substrate) because they bind somewhere other than the active site . Some allosteric sites are similar to active sites, which are often located in deep grooves, somewhat buried in the protein structure, and contain a limited set of residues that provide a well defined binding site. Other allosteric sites are more like protein-protein interfaces (PPIs), which have less rigid binding requirements, frequently have species-specific variations in composition, and have overall greater structural flexibility.
BMC cancer, Jan 28, 2015
Overexpression or mutation of the epidermal growth factor receptor (EGFR) potently enhances the g... more Overexpression or mutation of the epidermal growth factor receptor (EGFR) potently enhances the growth of many solid tumors. Tumor cells frequently display resistance to mechanistically-distinct EGFR-directed therapeutic agents, making it valuable to develop therapeutics that work by additional mechanisms. Current EGFR-targeting therapeutics include antibodies targeting the extracellular domains, and small molecules inhibiting the intracellular kinase domain. Recent studies have identified a novel prone extracellular tetrameric EGFR configuration, which we identify as a potential target for drug discovery. Our focus is on the prone EGFR tetramer, which contains a novel protein-protein interface involving extracellular domain III. This EGFR tetramer is computationally targeted for stabilization by small molecule ligand binding. This study performed virtual screening of a Life Chemicals, Inc. small molecule library of 345,232 drug-like compounds against a molecular dynamics simulation...
Biochemistry, 1994
Page 1. 11554 Biochemistry 1994, 33, 1 1554-1 1562 5-Chloro[ 1 ,4-13C]le~~linic Acid Modification... more Page 1. 11554 Biochemistry 1994, 33, 1 1554-1 1562 5-Chloro[ 1 ,4-13C]le~~linic Acid Modification of Mammalian and Bacterial Porphobilinogen Synthase Suggests an Active Site Containing Two Zn( II)+ Eileen K. Jaffe,' Marina ...