2gqs
From Proteopedia
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'''SAICAR Synthetase Complexed with CAIR-Mg2+ and ADP''' | '''SAICAR Synthetase Complexed with CAIR-Mg2+ and ADP''' | ||
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[[Category: Ginder, N D.]] | [[Category: Ginder, N D.]] | ||
[[Category: Honzatko, R B.]] | [[Category: Honzatko, R B.]] | ||
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| - | [[Category: | + | [[Category: Magnesium coordination]] |
| - | [[Category: | + | [[Category: Metal coordination]] |
| - | [[Category: | + | [[Category: Nucleotide complex]] |
| - | [[Category: | + | [[Category: Purc]] |
| - | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun May 4 05:24:54 2008'' | |
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | + | |
Revision as of 02:24, 4 May 2008
SAICAR Synthetase Complexed with CAIR-Mg2+ and ADP
Overview
Phosphoribosylaminoimidazole-succinocarboxamide synthetase (SAICAR synthetase) converts 4-carboxy-5-aminoimidazole ribonucleotide (CAIR) to 4-(N-succinylcarboxamide)-5-aminoimidazole ribonucleotide (SAICAR). The enzyme is a target of natural products that impair cell growth. Reported here are the crystal structures of the ADP and the ADP.CAIR complexes of SAICAR synthetase from Escherichia coli, the latter being the first instance of a CAIR-ligated SAICAR synthetase. ADP and CAIR bind to the active site in association with three Mg(2+), two of which coordinate the same oxygen atom of the 4-carboxyl group of CAIR; whereas, the third coordinates the alpha- and beta-phosphoryl groups of ADP. The ADP.CAIR complex is the basis for a transition state model of a phosphoryl transfer reaction involving CAIR and ATP, but also supports an alternative chemical pathway in which the nucleophilic attack of l-aspartate precedes the phosphoryl transfer reaction. The polypeptide fold for residues 204-221 of the E. coli structure differs significantly from those of the ligand-free SAICAR synthetase from Thermatoga maritima and the adenine nucleotide complexes of the synthetase from Saccharomyces cerevisiae. Conformational differences between the E. coli, T. maritima, and yeast synthetases suggest the possibility of selective inhibition of de novo purine nucleotide biosynthesis in microbial organisms.
About this Structure
2GQS is a Single protein structure of sequence from Escherichia coli. Full crystallographic information is available from OCA.
Reference
Nucleotide complexes of Escherichia coli phosphoribosylaminoimidazole succinocarboxamide synthetase., Ginder ND, Binkowski DJ, Fromm HJ, Honzatko RB, J Biol Chem. 2006 Jul 28;281(30):20680-8. Epub 2006 May 9. PMID:16687397 Page seeded by OCA on Sun May 4 05:24:54 2008
