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Non‐discriminating and discriminating aspartyl‐tRNA synthetases differ in the anticodon‐binding domain
Author(s) -
Charron Christophe,
Roy Hervé,
Blaise Mickael,
Giegé Richard,
Kern Daniel
Publication year - 2003
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/cdg148
Subject(s) - thermus thermophilus , biology , transfer rna , thermus , biochemistry , genetics , computational biology , rna , escherichia coli , thermophile , gene , enzyme
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 Å 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 β‐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.