1ady
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(New page: 200px<br /><applet load="1ady" size="450" color="white" frame="true" align="right" spinBox="true" caption="1ady, resolution 2.8Å" /> '''HISTIDYL-TRNA SYNTHET...)
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Revision as of 08:39, 20 November 2007
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HISTIDYL-TRNA SYNTHETASE IN COMPLEX WITH HISTIDYL-ADENYLATE
Overview
The crystal structure at 2.7 A resolution of histidyl-tRNA synthetase, (HisRS) from Thermus thermophilus in complex with its amino acid substrate, histidine has been determined. In the crystal asymmetric unit there are, two homodimers, each subunit containing 421 amino acid residues. Each, monomer of the enzyme consists of three domains: (1) an N-terminal, catalytic domain containing a six-stranded antiparallel beta-sheet and the, three motifs common to all class II aminoacyl-tRNA synthetases, (2) a, 90-residue C-terminal alpha/beta domain which is common to most class IIa, synthetases and is probably involved in recognizing the anticodon, stem-loop of tRNA(His), and (3) a HisRS-specific alpha-helical domain, inserted into the catalytic domain, between motifs II and III. The, position of the insertion domain above the catalytic site suggests that it, could clamp onto the acceptor stem of the tRNA during aminoacylation. Two, HisRS-specific peptides, 259-RGLDYY and 285-GGRYDG, are intimately, involved in forming the binding site for the histidine, a molecule of, which is found in the active site of each monomer. The structure of HisRS, in complex with histidyl adenylate, produced enzymatically in the crystal, has been determined at 3.2 A resolution. This structure shows that the, HisRS-specific Arg-259 interacts directly with the alpha-phosphate of the, adenylate on the opposite side to the usual conserved motif 2 arginine., Arg-259 thus substitutes for the divalent cation observed in seryl-tRNA, synthetase and plays a crucial catalytic role in the mechanism of, histidine activation.
About this Structure
1ADY is a Single protein structure of sequence from Thermus thermophilus with SO4 and HAM as ligands. Active as Histidine--tRNA ligase, with EC number 6.1.1.21 Full crystallographic information is available from OCA.
Reference
Crystal structure analysis of the activation of histidine by Thermus thermophilus histidyl-tRNA synthetase., Aberg A, Yaremchuk A, Tukalo M, Rasmussen B, Cusack S, Biochemistry. 1997 Mar 18;36(11):3084-94. PMID:9115984
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