Non-discriminating and discriminating aspartyl-tRNA synthetases differ in the anticodon-binding domain.
EMBO J
; 22(7): 1632-43, 2003 Apr 01.
Article
em En
| MEDLINE
| ID: mdl-12660169
ABSTRACT
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.
Texto completo:
1
Base de dados:
MEDLINE
Assunto principal:
Aspartato-tRNA Ligase
/
Anticódon
Tipo de estudo:
Prognostic_studies
Idioma:
En
Ano de publicação:
2003
Tipo de documento:
Article