1n9w
From Proteopedia
Crystal structure of the non-discriminating and archaeal-type aspartyl-tRNA synthetase from Thermus thermophilus
Overview
In most organisms, tRNA aminoacylation is ensured by 20 aminoacyl-tRNA synthetases (aaRSs). In eubacteria, however, synthetases can be duplicated as in Thermus thermophilus, which contains two distinct AspRSs. While AspRS-1 is specific, AspRS-2 is non-discriminating and aspartylates tRNA(Asp) and tRNA(Asn). The structure at 2.3 A resolution of AspRS-2, the first of a non-discriminating synthetase, was solved. It differs from that of AspRS-1 but has resemblance to that of discriminating and archaeal AspRS from Pyrococcus kodakaraensis. The protein presents non-conventional features in its OB-fold anticodon-binding domain, namely the absence of a helix inserted between two beta-strands of this fold and a peculiar L1 loop differing from the large loops known to interact with tRNA(Asp) identity determinant C36 in conventional AspRSs. In AspRS-2, this loop is small and structurally homologous to that in AsnRSs, including conservation of a proline. In discriminating Pyrococcus AspRS, the L1 loop, although small, lacks this proline and is not superimposable with that of AspRS-2 or AsnRS. Its particular status is demonstrated by a loop-exchange experiment that renders the Pyrococcus AspRS non-discriminating.
About this Structure
1N9W is a Single protein structure of sequence from Thermus thermophilus. Full crystallographic information is available from OCA.
Reference
Non-discriminating and discriminating aspartyl-tRNA synthetases differ in the anticodon-binding domain., Charron C, Roy H, Blaise M, Giege R, Kern D, EMBO J. 2003 Apr 1;22(7):1632-43. PMID:12660169 Page seeded by OCA on Sat May 3 02:16:30 2008
