1CG1

STRUCTURE OF THE MUTANT (K16Q) OF ADENYLOSUCCINATE SYNTHETASE FROM E. COLI COMPLEXED WITH HADACIDIN, GDP, 6-PHOSPHORYL-IMP, AND MG2+

Summary for 1CG1

• Entry DOI: 10.2210/pdb1cg1/pdb
• Descriptor: PROTEIN (ADENYLOSUCCINATE SYNTHETASE), MAGNESIUM ION, HADACIDIN, ... (6 entities in total)
• Functional Keywords: ligase, gtp-hydrolysing enzymes, purine 2 nucleotide biosynthesis, 6-phosporyl-imp
• Biological source: Escherichia coli K12
• Cellular location: Cytoplasm: P0A7D4
• Total number of polymer chains: 1
• Total formula weight: 48283.32

Authors

Choe, J.Y.,Poland, B.W.,Fromm, H.,Honzatko, R. (deposition date: 1999-03-26, release date: 1999-06-17, Last modification date: 2023-08-09)

Primary citation

Choe, J.Y.,Poland, B.W.,Fromm, H.J.,Honzatko, R.B.
Mechanistic implications from crystalline complexes of wild-type and mutant adenylosuccinate synthetases from Escherichia coli.
Biochemistry, 38:6953-6961, 1999

PubMed Abstract: 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.

PubMed: 10346917
DOI: 10.1021/bi990159s

Experimental method

X-RAY DIFFRACTION (2.5 Å)