1CG0 image
Entry Detail
PDB ID:
1CG0
Keywords:
Title:
STRUCTURE OF ADENYLOSUCCINATE SYNTHETASE FROM E. COLI COMPLEXED WITH HADACIDIN, GDP, 6-PHOSPHORYL-IMP, AND MG2+
Biological Source:
Source Organism:
Host Organism:
PDB Version:
Deposition Date:
1999-03-26
Release Date:
1999-06-17
Method Details:
Experimental Method:
Resolution:
2.50 Å
R-Value Free:
0.25
R-Value Work:
0.16
Space Group:
P 32 2 1
Macromolecular Entities
Polymer Type:polypeptide(L)
Description:PROTEIN (ADENYLOSUCCINATE SYNTHETASE)
Chain IDs:A
Chain Length:431
Number of Molecules:1
Biological Source:Escherichia coli K12
Primary Citation
Mechanistic implications from crystalline complexes of wild-type and mutant adenylosuccinate synthetases from Escherichia coli.
Biochemistry 38 6953 6961 (1999)
PMID: 10346917 DOI: 10.1021/bi990159s

Abstact

Asp13 and His41 are essential residues of adenylosuccinate synthetase, putatively catalyzing the formation of adenylosuccinate from an intermediate of 6-phosphoryl-IMP. Wild-type adenylosuccinate synthetase and three mutant synthetases (Arg143 --> Leu, Lys16 --> Gln, and Arg303 --> Leu) from Eschericha coli have been crystallized in the presence of IMP, hadacidin (an analogue of L-aspartate), Mg2+, and GTP. The active site of each complex contains 6-phosphoryl-IMP, Mg2+, GDP, and hadacidin, except for the Arg303 --> Leu mutant, which does not bind hadacidin. In response to the formation of 6-phosphoryl-IMP, Asp13 enters the inner coordination sphere of the active site Mg2+. His41 hydrogen bonds with 6-phosphoryl-IMP, except in the Arg303 --> Leu complex, where it remains bound to the guanine nucleotide. Hence, recognition of the active site Mg2+ by Asp13 evidently occurs after the formation of 6-phosphoryl-IMP, but recognition of the intermediate by His41 may require the association of L-aspartate with the active site. Structures reported here support a mechanism in which Asp13 and His41 act as the catalytic base and acid, respectively, in the formation of 6-phosphoryl-IMP, and then act together as catalytic acids in the subsequent formation of adenylosuccinate.

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