4A1O image
Entry Detail
PDB ID:
4A1O
Title:
Crystal structure of Mycobacterium tuberculosis PurH complexed with AICAR and a novel nucleotide CFAIR, at 2.48 A resolution.
Biological Source:
Host Organism:
PDB Version:
Deposition Date:
2011-09-17
Release Date:
2011-09-28
Method Details:
Experimental Method:
Resolution:
2.48 Å
R-Value Free:
0.22
R-Value Work:
0.18
R-Value Observed:
0.18
Space Group:
P 21 21 21
Macromolecular Entities
Polymer Type:polypeptide(L)
Description:BIFUNCTIONAL PURINE BIOSYNTHESIS PROTEIN PURH
Chain IDs:A, B
Chain Length:523
Number of Molecules:2
Biological Source:MYCOBACTERIUM TUBERCULOSIS
Primary Citation
Structural Analyses of a Purine Biosynthetic Enzyme from Mycobacterium Tuberculosis Reveal a Novel Bound Nucleotide.
J.Biol.Chem. 286 40706 ? (2011)
PMID: 21956117 DOI: 10.1074/JBC.M111.291138

Abstact

Enzymes of the de novo purine biosynthetic pathway have been identified as essential for the growth and survival of Mycobacterium tuberculosis and thus have potential for the development of anti-tuberculosis drugs. The final two steps of this pathway are carried out by the bifunctional enzyme 5-aminoimidazole-4-carboxamide ribonucleotide transformylase/inosine monophosphate cyclohydrolase (ATIC), also known as PurH. This enzyme has already been the target of anti-cancer drug development. We have determined the crystal structures of the M. tuberculosis ATIC (Rv0957) both with and without the substrate 5-aminoimidazole-4-carboxamide ribonucleotide, at resolutions of 2.5 and 2.2 Å, respectively. As for other ATIC enzymes, the protein is folded into two domains, the N-terminal domain (residues 1-212) containing the cyclohydrolase active site and the C-terminal domain (residues 222-523) containing the formyltransferase active site. An adventitiously bound nucleotide was found in the cyclohydrolase active site in both structures and was identified by NMR and mass spectral analysis as a novel 5-formyl derivative of an earlier intermediate in the biosynthetic pathway 4-carboxy-5-aminoimidazole ribonucleotide. This result and other studies suggest that this novel nucleotide is a cyclohydrolase inhibitor. The dimer formed by M. tuberculosis ATIC is different from those seen for human and avian ATICs, but it has a similar ∼50-Å separation of the two active sites of the bifunctional enzyme. Evidence in M. tuberculosis ATIC for reactivity of half-the-sites in the cyclohydrolase domains can be attributed to ligand-induced movements that propagate across the dimer interface and may be a common feature of ATIC enzymes.

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