1h4t
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PROLYL-TRNA SYNTHETASE FROM THERMUS THERMOPHILUS COMPLEXED WITH L-PROLINE
OverviewOverview
We describe the recognition by Thermus thermophilus prolyl-tRNA synthetase, (ProRSTT) of proline, ATP and prolyl-adenylate and the sequential, conformational changes occurring when the substrates bind and the, activated intermediate is formed. Proline and ATP binding cause, respectively conformational changes in the proline binding loop and motif, 2 loop. However formation of the activated intermediate is necessary for, the final conformational ordering of a ten residue peptide ("ordering, loop") close to the active site which would appear to be essential for, functional tRNA 3' end binding. These induced fit conformational changes, ensure that the enzyme is highly specific for proline activation and, aminoacylation. We also present new structures of apo and AMP bound, histidyl-tRNA synthetase (HisRS) from T. thermophilus which we compare to, our previous structures of the histidine and histidyl-adenylate bound, enzyme. Qualitatively, similar results to those observed with T., thermophilus prolyl-tRNA synthetase are found. However histidine binding, is sufficient to induce the co-operative ordering of the topologically, equivalent histidine binding loop and ordering loop. These two examples, contrast with most other class II aminoacyl-tRNA synthetases whose pocket, for the cognate amino acid side-chain is largely preformed. T., thermophilus prolyl-tRNA synthetase appears to be the second class II, aminoacyl-tRNA synthetase, after HisRS, to use a positively charged amino, acid instead of a divalent cation to catalyse the amino acid activation, reaction.
About this StructureAbout this Structure
1H4T is a Single protein structure of sequence from Thermus thermophilus with ZN and PRO as ligands. Active as Proline--tRNA ligase, with EC number 6.1.1.15 Structure known Active Sites: AC1, AC2, AC3, AC4, AC5, AC6, AC7 and AC8. Full crystallographic information is available from OCA.
ReferenceReference
A succession of substrate induced conformational changes ensures the amino acid specificity of Thermus thermophilus prolyl-tRNA synthetase: comparison with histidyl-tRNA synthetase., Yaremchuk A, Tukalo M, Grotli M, Cusack S, J Mol Biol. 2001 Jun 15;309(4):989-1002. PMID:11399074
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