1b7y
From Proteopedia
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PHENYLALANYL TRNA SYNTHETASE COMPLEXED WITH PHENYLALANINYL-ADENYLATE
Overview
The crystal structures of Thermus thermophilus phenylalanyl-tRNA, synthetase (PheRS) complexed with phenylalanine and, phenylalaninyl-adenylate (PheOH-AMP), the synthetic analogue of, phenylalanyl-adenylate, have been determined at 2.7A and 2.5A resolution, respectively. Both Phe and PheOH-AMP are engulfed in the active site cleft, of the catalytic alpha-subunit of PheRS, and neither makes contact with, the PheRS beta-subunit. The conformations and binding of Phe are almost, identical in both complexes. The recognition of Phe by PheRS is achieved, through a mixture of multiple van der Waals interactions and hydrogen, bonds. The side-chain of the Phe substrate is sandwiched between the, hydrophobic side-chains of Phealpha258 and Phealpha260 on one side, and, the main-chain atoms of the two adjacent beta-strands on the other. The, side-chains of Valalpha261 and Alaalpha314 form the back wall of the amino, acid binding pocket. In addition, PheRS residues (Trpalpha149, Seralpha180, Hisalpha178, Argalpha204, Glnalpha218, and Glualpha220) form, a total of seven hydrogen bonds with the main-chain atoms of Phe. The, conformation of PheOH-AMP and the network of interactions of its AMP, moiety with PheRS are reminiscent of the other class II synthetases. The, structural similarity between PheRS and histidyl-tRNA synthetase extends, to the amino acid binding site, which is normally unique for each enzyme., The complex structures suggest that the PheRS beta-subunit may affect the, first step of the reaction (formation of phenylalanyl-adenylate) through, the metal-mediated conserved alpha/beta-subunit interface. The modeling of, tyrosine in the active site of PheRS revealed no apparent close contacts, between tyrosine and the PheRS residues. This result implies that the, proofreading mechanism against activated tyrosine, rather than direct, recognition, may play the major role in the PheRS specificity.
About this Structure
1B7Y is a Protein complex structure of sequences from Thermus thermophilus with MG and FYA as ligands. Active as Phenylalanine--tRNA ligase, with EC number 6.1.1.20 Full crystallographic information is available from OCA.
Reference
Crystal structures of phenylalanyl-tRNA synthetase complexed with phenylalanine and a phenylalanyl-adenylate analogue., Reshetnikova L, Moor N, Lavrik O, Vassylyev DG, J Mol Biol. 1999 Apr 2;287(3):555-68. PMID:10092459
Page seeded by OCA on Tue Nov 20 11:26:19 2007
