Structural and biochemical characterization of N(5)-carboxyaminoimidazole ribonucleotide synthetase and N(5)-carboxyaminoimidazole ribonucleotide mutase from Staphylococcus aureus.
Summary of "Structural and biochemical characterization of N(5)-carboxyaminoimidazole ribonucleotide synthetase and N(5)-carboxyaminoimidazole ribonucleotide mutase from Staphylococcus aureus."
With the rapid rise of methicillin-resistant Staphylococcus aureus infections, new strategies against S. aureus are urgently needed. De novo purine biosynthesis is a promising yet unexploited target, insofar as abundant evidence has shown that bacteria with compromised purine biosynthesis are attenuated. Fundamental differences exist within the process by which humans and bacteria convert 5-aminoimidazole ribonucleotide (AIR) to 4-carboxy-5-aminoimidazole ribonucleotide (CAIR). In bacteria, this transformation occurs through a two-step conversion catalyzed by PurK and PurE; in humans, it is mediated by a one-step conversion catalyzed by class II PurE. Thus, these bacterial enzymes are potential targets for selective antibiotic development. Here, the first comprehensive structural and biochemical characterization of PurK and PurE from S. aureus is presented. Structural analysis of S. aureus PurK reveals a nonconserved phenylalanine near the AIR-binding site that occupies the putative position of the imidazole ring of AIR. Mutation of this phenylalanine to isoleucine or tryptophan reduced the enzyme efficiency by around tenfold. The K(m) for bicarbonate was determined for the first time for a PurK enzyme and was found to be ∼18.8 mM. The structure of PurE is described in comparison to that of human class II PurE. It is confirmed biochemically that His38 is essential for function. These studies aim to provide foundations for future structure-based drug-discovery efforts against S. aureus purine biosynthesis.
Affiliation
Department of Chemistry and Institute for Biophysical Dynamics, The University of Chicago, 929 East 57th Street, GCIS E321, Chicago, IL 60637, USA.
Journal Details
This article was published in the following journal.
Name: Acta crystallographica. Section D, Biological crystallography
ISSN: 1399-0047
Pages: 707-15
Links
- PubMed Source: http://www.ncbi.nlm.nih.gov/pubmed/21795812
- DOI: http://dx.doi.org/10.1107/S0907444911023821
Medical and Biotech [MESH] Definitions
Phosphoribosylaminoimidazolecarboxamide Formyltransferase
An enzyme that catalyzes the conversion of aminoimidazole-4-carboxamide ribonucleotide to 5-formyl-aminoimidazole-4-carboxamide ribonucleotide in the purine de novo synthesis pathway. It requires the cofactor N(10)-FORMYLTETRAHYDROFOLATE as the formyl donor.
Thioredoxins
Hydrogen-donating proteins that participates in a variety of biochemical reactions including ribonucleotide reduction and reduction of PEROXIREDOXINS. Thioredoxin is oxidized from a dithiol to a disulfide when acting as a reducing cofactor. The disulfide form is then reduced by NADPH in a reaction catalyzed by THIOREDOXIN REDUCTASE.
Exonucleases
Enzymes that catalyze the release of mononucleotides by the hydrolysis of the terminal bond of deoxyribonucleotide or ribonucleotide chains.
Trna Methyltransferases
Enzymes that catalyze the S-adenosyl-L-methionine-dependent methylation of ribonucleotide bases within a transfer RNA molecule. EC 2.1.1.
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