Abstract
Purine metabolism plays a major role in regulating the availability of purine nucleotides destined for nucleic acid synthesis. Allantoate amidohydrolase catalyzes the conversion of allantoate to (S)-ureidoglycolate, one of the crucial alternate steps in purine metabolism. The crystal structure of a ternary complex of allantoate amidohydrolase with its substrate allantoate and an allosteric effector, a sulfate ion, from Escherichia coli was determined to understand better the catalytic mechanism and substrate specificity. The 2.25 Å resolution X-ray structure reveals an α/β scaffold akin to zinc exopeptidases of the peptidase M20 family and lacks the (β/α)8-barrel fold characteristic of the amidohydrolases. Arrangement of the substrate and the two co-catalytic zinc ions at the active site governs catalytic specificity for hydrolysis of N-carbamyl versus the peptide bond in exopeptidases. In its crystalline form, allantoate amidohydrolase adopts a relatively open conformation. However, structural analysis reveals the possibility of a significant movement of domains via rotation about two hinge regions upon allosteric effector and substrate binding resulting in a closed catalytically competent conformation by bringing the substrate allantoate closer to co-catalytic zinc ions. Two cis-prolyl peptide bonds found on either side of the dimerization domain in close proximity to the substrate and ligand-binding sites may be involved in protein folding and in preserving the integrity of the catalytic site.
Original language | English (US) |
---|---|
Pages (from-to) | 450-463 |
Number of pages | 14 |
Journal | Journal of molecular biology |
Volume | 368 |
Issue number | 2 |
DOIs | |
State | Published - Apr 27 2007 |
Externally published | Yes |
All Science Journal Classification (ASJC) codes
- Structural Biology
- Molecular Biology
Keywords
- allantoate amidohydrolase
- allosteric effector
- crystal structure
- di-zinc-dependent exopeptidases
- hinge region