1evl
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CRYSTAL STRUCTURE OF A TRUNCATED FORM OF THREONYL-TRNA SYNTHETASE WITH A THREONYL ADENYLATE ANALOG
OverviewOverview
Accurate translation of the genetic code depends on the ability of aminoacyl-tRNA synthetases to distinguish between similar amino acids. In order to investigate the basis of amino acid recognition and to understand the role played by the zinc ion present in the active site of threonyl-tRNA synthetase, we have determined the crystal structures of complexes of an active truncated form of the enzyme with a threonyl adenylate analog or threonine. The zinc ion is directly involved in threonine recognition, forming a pentacoordinate intermediate with both the amino group and the side chain hydroxyl. Amino acid activation experiments reveal that the enzyme shows no activation of isosteric valine, and activates serine at a rate 1,000-fold less than that of cognate threonine. This study demonstrates that the zinc ion is neither strictly catalytic nor structural and suggests how the zinc ion ensures that only amino acids that possess a hydroxyl group attached to the beta-position are activated.
About this StructureAbout this Structure
1EVL is a Single protein structure of sequence from Escherichia coli with and as ligands. Active as Threonine--tRNA ligase, with EC number 6.1.1.3 Full crystallographic information is available from OCA.
ReferenceReference
Zinc ion mediated amino acid discrimination by threonyl-tRNA synthetase., Sankaranarayanan R, Dock-Bregeon AC, Rees B, Bovee M, Caillet J, Romby P, Francklyn CS, Moras D, Nat Struct Biol. 2000 Jun;7(6):461-5. PMID:10881191
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