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| {{STRUCTURE_1cg3| PDB=1cg3 | SCENE= }} | | {{STRUCTURE_1cg3| PDB=1cg3 | SCENE= }} |
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| '''STRUCTURE OF THE MUTANT (R143L) OF ADENYLOSUCCINATE SYNTHETASE FROM E. COLI COMPLEXED WITH HADACIDIN, GDP, 6-PHOSPHORYL-IMP, AND MG2+'''
| | ===STRUCTURE OF THE MUTANT (R143L) OF ADENYLOSUCCINATE SYNTHETASE FROM E. COLI COMPLEXED WITH HADACIDIN, GDP, 6-PHOSPHORYL-IMP, AND MG2+=== |
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| ==Overview==
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| 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.
| | The line below this paragraph, {{ABSTRACT_PUBMED_10346917}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 10346917 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_10346917}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Ligase]] | | [[Category: Ligase]] |
| [[Category: Purine 2 nucleotide biosynthesis]] | | [[Category: Purine 2 nucleotide biosynthesis]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 12:41:59 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jun 30 20:42:01 2008'' |
