3K5H

Crystal structure of carboxyaminoimidazole ribonucleotide synthase from asperigillus clavatus complexed with ATP

Summary for 3K5H

• Entry DOI: 10.2210/pdb3k5h/pdb
• Related: 3K5I
• Descriptor: Phosphoribosyl-aminoimidazole carboxylase, ADENOSINE-5'-TRIPHOSPHATE, MAGNESIUM ION, ... (4 entities in total)
• Functional Keywords: purine biosynthesis, atp-grasp, lyase
• Biological source: Aspergillus clavatus
• Total number of polymer chains: 4
• Total formula weight: 181106.51

Authors

Thoden, J.B.,Holden, H.M.,Paritala, H.,Firestine, S.M. (deposition date: 2009-10-07, release date: 2009-10-20, Last modification date: 2024-04-03)

Primary citation

Thoden, J.B.,Holden, H.M.,Paritala, H.,Firestine, S.M.
Structural and functional studies of Aspergillus clavatus N(5)-carboxyaminoimidazole ribonucleotide synthetase
Biochemistry, 49:752-760, 2010

PubMed Abstract: N(5)-Carboxyaminoimidazole ribonucleotide synthetase (N(5)-CAIR synthetase), a key enzyme in microbial de novo purine biosynthesis, catalyzes the conversion of aminoimidazole ribonucleotide (AIR) to N(5)-CAIR. To date, this enzyme has been observed only in microorganisms, and thus, it represents an ideal target for antimicrobial drug development. Here we report the cloning, crystallization, and three-dimensional structural analysis of Aspergillus clavatus N(5)-CAIR synthetase solved in the presence of either Mg(2)ATP or MgADP and AIR. These structures, determined to 2.1 and 2.0 A, respectively, revealed that AIR binds in a pocket analogous to that observed for other ATP-grasp enzymes involved in purine metabolism. On the basis of these models, a site-directed mutagenesis study was subsequently conducted that focused on five amino acid residues located in the active site region of the enzyme. These investigations demonstrated that Asp 153 and Lys 353 play critical roles in catalysis without affecting substrate binding. All other mutations affected substrate binding and, in some instances, catalysis as well. Taken together, the structural and kinetic data presented here suggest a catalytic mechanism whereby Mg(2)ATP and bicarbonate first react to form the unstable intermediate carboxyphosphate. This intermediate subsequently decarboxylates to CO(2) and inorganic phosphate, and the amino group of AIR, through general base assistance by Asp 153, attacks CO(2) to form N(5)-CAIR.

PubMed: 20050602
DOI: 10.1021/bi901599u

Experimental method

X-RAY DIFFRACTION (2.1 Å)