1li5
From Proteopedia
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Crystal Structure of Cysteinyl-tRNA Synthetase
Overview
Cysteinyl-tRNA synthetase (CysRS) is highly specific for synthesis of, cysteinyl adenylate, yet does not possess the amino acid editing activity, characteristic of many other tRNA synthetases. To elucidate how CysRS is, able to distinguish cysteine from non-cognate amino acids, crystal, structures of the Escherichia coli enzyme were determined in apo and, cysteine-bound states. The structures reveal that the substrate cysteine, thiolate forms a single direct interaction with a zinc ion bound at the, base of the active site cleft, in a trigonal bipyramidal geometry together, with four highly conserved protein side chains. Cysteine binding induces, movement of the zinc ion towards substrate, as well as flipping of the, conserved Trp205 indole ring to pack on the thiol side chain. The, imidazole groups of five conserved histidines lie adjacent to the zinc, ion, forming a unique arrangement suggestive of functional significance., Thus, amino acid discrimination without editing arises most directly from, the favorable zinc-thiolate interaction, which is not possible for, non-cognate substrates. Additional selectivity may be generated during the, induced-fit conformational changes that help assemble the active site.
About this Structure
1LI5 is a Single protein structure of sequence from Escherichia coli with as ligand. Active as Cysteine--tRNA ligase, with EC number 6.1.1.16 Full crystallographic information is available from OCA.
Reference
Structural origins of amino acid selection without editing by cysteinyl-tRNA synthetase., Newberry KJ, Hou YM, Perona JJ, EMBO J. 2002 Jun 3;21(11):2778-87. PMID:12032090
Page seeded by OCA on Wed Jan 23 15:29:40 2008
