1kmn
From Proteopedia
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==Overview== | ==Overview== | ||
| - | The crystal structure of an enzyme-substrate complex with histidyl-tRNA | + | The crystal structure of an enzyme-substrate complex with histidyl-tRNA synthetase from Escherichia coli, ATP, and the amino acid analog histidinol is described and compared with the previously obtained enzyme-product complex with histidyl-adenylate. An active site arginine, Arg-259, unique to all histidyl-tRNA synthetases, plays the role of the catalytic magnesium ion seen in seryl-tRNA synthetase. When Arg-259 is substituted with histidine, the apparent second order rate constant (kcat/Km) for the pyrophosphate exchange reaction and the aminoacylation reaction decreases 1,000-fold and 500-fold, respectively. Crystals soaked with MnCl2 reveal the existence of two metal binding sites between beta- and gamma-phosphates; these sites appear to stabilize the conformation of the pyrophosphate. The use of both conserved metal ions and arginine in phosphoryl transfer provides evidence of significant early functional divergence of class II aminoacyl-tRNA synthetases. |
==About this Structure== | ==About this Structure== | ||
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[[Category: Histidine--tRNA ligase]] | [[Category: Histidine--tRNA ligase]] | ||
[[Category: Single protein]] | [[Category: Single protein]] | ||
| - | [[Category: Arnez, J | + | [[Category: Arnez, J G.]] |
| - | [[Category: Francklyn, C | + | [[Category: Francklyn, C S.]] |
[[Category: Moras, D.]] | [[Category: Moras, D.]] | ||
[[Category: ATP]] | [[Category: ATP]] | ||
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[[Category: synthetase]] | [[Category: synthetase]] | ||
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 13:35:45 2008'' |
Revision as of 11:35, 21 February 2008
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HISTIDYL-TRNA SYNTHETASE COMPLEXED WITH HISTIDINOL AND ATP
Overview
The crystal structure of an enzyme-substrate complex with histidyl-tRNA synthetase from Escherichia coli, ATP, and the amino acid analog histidinol is described and compared with the previously obtained enzyme-product complex with histidyl-adenylate. An active site arginine, Arg-259, unique to all histidyl-tRNA synthetases, plays the role of the catalytic magnesium ion seen in seryl-tRNA synthetase. When Arg-259 is substituted with histidine, the apparent second order rate constant (kcat/Km) for the pyrophosphate exchange reaction and the aminoacylation reaction decreases 1,000-fold and 500-fold, respectively. Crystals soaked with MnCl2 reveal the existence of two metal binding sites between beta- and gamma-phosphates; these sites appear to stabilize the conformation of the pyrophosphate. The use of both conserved metal ions and arginine in phosphoryl transfer provides evidence of significant early functional divergence of class II aminoacyl-tRNA synthetases.
About this Structure
1KMN is a Single protein structure of sequence from Escherichia coli with and as ligands. Active as Histidine--tRNA ligase, with EC number 6.1.1.21 Known structural/functional Sites: , , and . Full crystallographic information is available from OCA.
Reference
The first step of aminoacylation at the atomic level in histidyl-tRNA synthetase., Arnez JG, Augustine JG, Moras D, Francklyn CS, Proc Natl Acad Sci U S A. 1997 Jul 8;94(14):7144-9. PMID:9207058
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