1j4b
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(New page: 200px<br /><applet load="1j4b" size="450" color="white" frame="true" align="right" spinBox="true" caption="1j4b, resolution 2.50Å" /> '''Recombinant Mouse-Mu...) |
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caption="1j4b, resolution 2.50Å" /> | caption="1j4b, resolution 2.50Å" /> | ||
'''Recombinant Mouse-Muscle Adenylosuccinate Synthetase'''<br /> | '''Recombinant Mouse-Muscle Adenylosuccinate Synthetase'''<br /> | ||
==Overview== | ==Overview== | ||
| - | Vertebrates possess two isozymes of adenylosuccinate synthetase. The | + | Vertebrates possess two isozymes of adenylosuccinate synthetase. The acidic isozyme is similar to the synthetase from bacteria and plants, being involved in the de novo biosynthesis of AMP, whereas the basic isozyme participates in the purine nucleotide cycle. Reported here is the first instance of overexpression and crystal structure determination of a basic isozyme of adenylosuccinate synthetase. The recombinant mouse muscle enzyme purified to homogeneity in milligram quantities exhibits a specific activity comparable with that of the rat muscle enzyme isolated from tissue and K(m) parameters for GTP, IMP, and l-aspartate (12, 45, and 140 microm, respectively) similar to those of the enzyme from Escherichia coli. The mouse muscle and E. coli enzymes have similar polypeptide folds, differing primarily in the conformation of loops, involved in substrate recognition and stabilization of the transition state. Residues 65-68 of the muscle isozyme adopt a conformation not observed in any previous synthetase structure. In its new conformation, segment 65-68 forms intramolecular hydrogen bonds with residues essential for the recognition of IMP and, in fact, sterically excludes IMP from the active site. Observed differences in ligand recognition among adenylosuccinate synthetases may be due in part to conformational variations in the IMP pocket of the ligand-free enzymes. |
==About this Structure== | ==About this Structure== | ||
| - | 1J4B is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Mus_musculus Mus musculus]. Active as [http://en.wikipedia.org/wiki/Adenylosuccinate_synthase Adenylosuccinate synthase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=6.3.4.4 6.3.4.4] Full crystallographic information is available from [http:// | + | 1J4B is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Mus_musculus Mus musculus]. Active as [http://en.wikipedia.org/wiki/Adenylosuccinate_synthase Adenylosuccinate synthase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=6.3.4.4 6.3.4.4] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1J4B OCA]. |
==Reference== | ==Reference== | ||
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[[Category: Single protein]] | [[Category: Single protein]] | ||
[[Category: Borza, T.]] | [[Category: Borza, T.]] | ||
| - | [[Category: Choe, J | + | [[Category: Choe, J Y.]] |
| - | [[Category: Fromm, H | + | [[Category: Fromm, H J.]] |
| - | [[Category: Honzatko, R | + | [[Category: Honzatko, R B.]] |
| - | [[Category: Iancu, C | + | [[Category: Iancu, C V.]] |
[[Category: gtp-hydrolyzing enzymes]] | [[Category: gtp-hydrolyzing enzymes]] | ||
[[Category: ligase]] | [[Category: ligase]] | ||
[[Category: purine nucleotide cycle]] | [[Category: purine nucleotide cycle]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 13:18:46 2008'' |
Revision as of 11:18, 21 February 2008
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Recombinant Mouse-Muscle Adenylosuccinate Synthetase
Overview
Vertebrates possess two isozymes of adenylosuccinate synthetase. The acidic isozyme is similar to the synthetase from bacteria and plants, being involved in the de novo biosynthesis of AMP, whereas the basic isozyme participates in the purine nucleotide cycle. Reported here is the first instance of overexpression and crystal structure determination of a basic isozyme of adenylosuccinate synthetase. The recombinant mouse muscle enzyme purified to homogeneity in milligram quantities exhibits a specific activity comparable with that of the rat muscle enzyme isolated from tissue and K(m) parameters for GTP, IMP, and l-aspartate (12, 45, and 140 microm, respectively) similar to those of the enzyme from Escherichia coli. The mouse muscle and E. coli enzymes have similar polypeptide folds, differing primarily in the conformation of loops, involved in substrate recognition and stabilization of the transition state. Residues 65-68 of the muscle isozyme adopt a conformation not observed in any previous synthetase structure. In its new conformation, segment 65-68 forms intramolecular hydrogen bonds with residues essential for the recognition of IMP and, in fact, sterically excludes IMP from the active site. Observed differences in ligand recognition among adenylosuccinate synthetases may be due in part to conformational variations in the IMP pocket of the ligand-free enzymes.
About this Structure
1J4B is a Single protein structure of sequence from Mus musculus. Active as Adenylosuccinate synthase, with EC number 6.3.4.4 Full crystallographic information is available from OCA.
Reference
Recombinant mouse muscle adenylosuccinate synthetase: overexpression, kinetics, and crystal structure., Iancu CV, Borza T, Choe JY, Fromm HJ, Honzatko RB, J Biol Chem. 2001 Nov 9;276(45):42146-52. Epub 2001 Sep 17. PMID:11560929
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