1d2r
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(New page: 200px<br /><applet load="1d2r" size="450" color="white" frame="true" align="right" spinBox="true" caption="1d2r, resolution 2.90Å" /> '''2.9 A CRYSTAL STRUCT...)
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Revision as of 10:51, 20 November 2007
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2.9 A CRYSTAL STRUCTURE OF LIGAND-FREE TRYPTOPHANYL-TRNA SYNTHETASE: DOMAIN MOVEMENTS FRAGMENT THE ADENINE NUCLEOTIDE BINDING SITE.
Overview
The crystal structure of ligand-free tryptophanyl-tRNA synthetase (TrpRS), was solved at 2.9 A using a combination of molecular replacement and, maximum-entropy map/phase improvement. The dimeric structure (R = 23.7, Rfree = 26.2) is asymmetric, unlike that of the TrpRS tryptophanyl-5'AMP, complex (TAM; Doublie S, Bricogne G, Gilmore CJ, Carter CW Jr, 1995, Structure 3:17-31). In agreement with small-angle solution X-ray, scattering experiments, unliganded TrpRS has a conformation in which both, monomers open, leaving only the tryptophan-binding regions of their active, sites intact. The amino terminal alphaA-helix, TIGN, and KMSKS signature, sequences, and the distal helical domain rotate as a single rigid body, away from the dinucleotide-binding fold domain, opening the AMP binding, site, seen in the TAM complex, into two halves. Comparison of side-chain, packing in ligand-free TrpRS and the TAM complex, using identification of, nonpolar nuclei (Ilyin VA, 1994, Protein Eng 7:1189-1195), shows that, significant repacking occurs between three relatively stable core regions, one of which acts as a bearing between the other two. These domain, rearrangements provide a new structural paradigm that is consistent in, detail with the "induced-fit" mechanism proposed for TyrRS by Fersht et, al. (Fersht AR, Knill-Jones JW, Beduelle H, Winter G, 1988, Biochemistry, 27:1581-1587). Coupling of ATP binding determinants associated with the, two catalytic signature sequences to the helical domain containing the, presumptive anticodon-binding site provides a mechanism to coordinate, active-site chemistry with relocation of the major tRNA binding, determinants.
About this Structure
1D2R is a Single protein structure of sequence from Geobacillus stearothermophilus. Active as Tryptophan--tRNA ligase, with EC number 6.1.1.2 Full crystallographic information is available from OCA.
Reference
2.9 A crystal structure of ligand-free tryptophanyl-tRNA synthetase: domain movements fragment the adenine nucleotide binding site., Ilyin VA, Temple B, Hu M, Li G, Yin Y, Vachette P, Carter CW Jr, Protein Sci. 2000 Feb;9(2):218-31. PMID:10716174
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