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| - | [[Image:2gcq.jpg|left|200px]] | + | {{Seed}} |
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| | {{STRUCTURE_2gcq| PDB=2gcq | SCENE= }} | | {{STRUCTURE_2gcq| PDB=2gcq | SCENE= }} |
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| - | '''Fully ligated E.Coli Adenylosuccinate Synthetase with GTP, 2'-deoxy-IMP and Hadacidin'''
| + | ===Fully ligated E.Coli Adenylosuccinate Synthetase with GTP, 2'-deoxy-IMP and Hadacidin=== |
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| - | ==Overview==
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| - | Adenylosuccinate synthetase catalyzes the first committed step in the de novo biosynthesis of AMP, coupling L-aspartate and IMP to form adenylosuccinate. Km values of IMP and 2'-deoxy-IMP are nearly identical with each substrate supporting comparable maximal velocities. Nonetheless, the Km value for L-aspartate and the Ki value for hadacidin (a competitive inhibitor with respect to L-aspartate) are 29-57-fold lower in the presence of IMP than in the presence of 2'-deoxy-IMP. Crystal structures of the synthetase ligated with hadacidin, GDP, and either 6-phosphoryl-IMP or 2'-deoxy-6-phosphoryl-IMP are identical except for the presence of a cavity normally occupied by the 2'-hydroxyl group of IMP. In the presence of 6-phosphoryl-IMP and GDP (hadacidin absent), the L-aspartate pocket can retain its fully ligated conformation, forming hydrogen bonds between the 2'-hydroxyl group of IMP and sequence-invariant residues. In the presence of 2'-deoxy-6-phosphoryl-IMP and GDP, however, the L-aspartate pocket is poorly ordered. The absence of the 2'-hydroxyl group of the deoxyribonucleotide may destabilize binding of the ligand to the L-aspartate pocket by disrupting hydrogen bonds that maintain a favorable protein conformation and by the introduction of a cavity into the fully ligated active site. At an approximate energy cost of 2.2 kcal/mol, the unfavorable thermodynamics of cavity formation may be the major factor in destabilizing ligands at the L-aspartate pocket.
| + | The line below this paragraph, {{ABSTRACT_PUBMED_16981730}}, adds the Publication Abstract to the page |
| | + | (as it appears on PubMed at http://www.pubmed.gov), where 16981730 is the PubMed ID number. |
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| | + | {{ABSTRACT_PUBMED_16981730}} |
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| | ==About this Structure== | | ==About this Structure== |
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| | [[Category: Gtp]] | | [[Category: Gtp]] |
| | [[Category: Hadacidin]] | | [[Category: Hadacidin]] |
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun May 4 04:57:28 2008'' | + | |
| | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 29 00:03:45 2008'' |
Revision as of 21:03, 28 July 2008
Template:STRUCTURE 2gcq
Fully ligated E.Coli Adenylosuccinate Synthetase with GTP, 2'-deoxy-IMP and Hadacidin
Template:ABSTRACT PUBMED 16981730
About this Structure
2GCQ is a Single protein structure of sequence from Escherichia coli. Full crystallographic information is available from OCA.
Reference
Cavitation as a mechanism of substrate discrimination by adenylosuccinate synthetases., Iancu CV, Zhou Y, Borza T, Fromm HJ, Honzatko RB, Biochemistry. 2006 Sep 26;45(38):11703-11. PMID:16981730
Page seeded by OCA on Tue Jul 29 00:03:45 2008
