1xff
From Proteopedia
(New page: 200px<br /><applet load="1xff" size="450" color="white" frame="true" align="right" spinBox="true" caption="1xff, resolution 1.80Å" /> '''Glutaminase domain o...) |
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'''Glutaminase domain of glucosamine 6-phosphate synthase complexed with glutamate'''<br /> | '''Glutaminase domain of glucosamine 6-phosphate synthase complexed with glutamate'''<br /> | ||
==Overview== | ==Overview== | ||
| - | BACKGROUND: Amidotransferases use the amide nitrogen of glutamine in a | + | BACKGROUND: Amidotransferases use the amide nitrogen of glutamine in a number of important biosynthetic reactions. They are composed of a glutaminase domain, which catalyzes the hydrolysis of glutamine to glutamate and ammonia, and a synthetase domain, catalyzing amination of the substrate. To gain insight into the mechanism of nitrogen transfer, we examined the structure of the glutaminase domain of glucosamine 6-phosphate synthase (GLMS). RESULTS: The crystal structures of the enzyme complexed with glutamate and with a competitive inhibitor, Glu-hydroxamate, have been determined to 1.8 A resolution. The protein fold has structural homology to other members of the superfamily of N-terminal nucleophile (Ntn) hydrolases, being a sandwich of antiparallel beta sheets surrounded by two layers of alpha helices. CONCLUSIONS: The structural homology between the glutaminase domain of GLMS and that of PRPP amidotransferase (the only other Ntn amidotransferase whose structure is known) indicates that they may have diverged from a common ancestor. Cys1 is the catalytic nucleophile in GLMS, and the nucleophilic character of its thiol group appears to be increased through general base activation by its own alpha-amino group. Cys1 can adopt two conformations, one active and one inactive; glutamine binding locks the residue in a predetermined conformation. We propose that when a nitrogen acceptor is present Cys1 is kept in the active conformation, explaining the phenomenon of substrate-induced activation of the enzyme, and that Arg26 is central in this coupling. |
==About this Structure== | ==About this Structure== | ||
| - | 1XFF is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli] with NA, ACT and GLU as [http://en.wikipedia.org/wiki/ligands ligands]. This structure | + | 1XFF is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli] with <scene name='pdbligand=NA:'>NA</scene>, <scene name='pdbligand=ACT:'>ACT</scene> and <scene name='pdbligand=GLU:'>GLU</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. This structure supersedes the now removed PDB entry 1GDO. Active as [http://en.wikipedia.org/wiki/Glutamine--fructose-6-phosphate_transaminase_(isomerizing) Glutamine--fructose-6-phosphate transaminase (isomerizing)], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.6.1.16 2.6.1.16] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1XFF OCA]. |
==Reference== | ==Reference== | ||
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[[Category: Glutamine--fructose-6-phosphate transaminase (isomerizing)]] | [[Category: Glutamine--fructose-6-phosphate transaminase (isomerizing)]] | ||
[[Category: Single protein]] | [[Category: Single protein]] | ||
| - | [[Category: Isupov, M | + | [[Category: Isupov, M N.]] |
[[Category: Teplyakov, A.]] | [[Category: Teplyakov, A.]] | ||
[[Category: ACT]] | [[Category: ACT]] | ||
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[[Category: complex (transferase/inhibitor); glutamine amidotransferase]] | [[Category: complex (transferase/inhibitor); glutamine amidotransferase]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 15:54:13 2008'' |
Revision as of 13:54, 21 February 2008
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Glutaminase domain of glucosamine 6-phosphate synthase complexed with glutamate
Overview
BACKGROUND: Amidotransferases use the amide nitrogen of glutamine in a number of important biosynthetic reactions. They are composed of a glutaminase domain, which catalyzes the hydrolysis of glutamine to glutamate and ammonia, and a synthetase domain, catalyzing amination of the substrate. To gain insight into the mechanism of nitrogen transfer, we examined the structure of the glutaminase domain of glucosamine 6-phosphate synthase (GLMS). RESULTS: The crystal structures of the enzyme complexed with glutamate and with a competitive inhibitor, Glu-hydroxamate, have been determined to 1.8 A resolution. The protein fold has structural homology to other members of the superfamily of N-terminal nucleophile (Ntn) hydrolases, being a sandwich of antiparallel beta sheets surrounded by two layers of alpha helices. CONCLUSIONS: The structural homology between the glutaminase domain of GLMS and that of PRPP amidotransferase (the only other Ntn amidotransferase whose structure is known) indicates that they may have diverged from a common ancestor. Cys1 is the catalytic nucleophile in GLMS, and the nucleophilic character of its thiol group appears to be increased through general base activation by its own alpha-amino group. Cys1 can adopt two conformations, one active and one inactive; glutamine binding locks the residue in a predetermined conformation. We propose that when a nitrogen acceptor is present Cys1 is kept in the active conformation, explaining the phenomenon of substrate-induced activation of the enzyme, and that Arg26 is central in this coupling.
About this Structure
1XFF is a Single protein structure of sequence from Escherichia coli with , and as ligands. This structure supersedes the now removed PDB entry 1GDO. Active as Glutamine--fructose-6-phosphate transaminase (isomerizing), with EC number 2.6.1.16 Full crystallographic information is available from OCA.
Reference
Substrate binding is required for assembly of the active conformation of the catalytic site in Ntn amidotransferases: evidence from the 1.8 A crystal structure of the glutaminase domain of glucosamine 6-phosphate synthase., Isupov MN, Obmolova G, Butterworth S, Badet-Denisot MA, Badet B, Polikarpov I, Littlechild JA, Teplyakov A, Structure. 1996 Jul 15;4(7):801-10. PMID:8805567
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