Naslov
Amino acid-dependent transfer RNA affinity in a class I aminoacyl-tRNA synthetase.

Autori
Uter, Nathan ; Gruić-Sovulj, Ita ; Perona, John

Izvornik
The Journal of biological chemistry (0021-9258) 280 (2005); 23966-23977

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
aminoacil-tRNA-sintetaze; transfer-RNA; glutamin
(aminoacyl-tRNA synthetase; transfer RNA; glutamine)

Sažetak
Steady-state and transient kinetic analyses of glutaminyl-tRNA synthetase (GlnRS) reveal that the enzyme discriminates against noncognate glutamate at multiple steps during the overall aminoacylation reaction. A major portion of the selectivity arises in the amino acid activation portion of the reaction, whereas the discrimination in the overall two-step reaction arises from very weak binding of noncognate glutamate. Further transient kinetics experiments showed that tRNA(Gln) binds to GlnRS approximately 60-fold weaker when noncognate glutamate is present and that glutamate reduces the association rate of tRNA with the enzyme by 100-fold. These findings demonstrate that amino acid and tRNA binding are interdependent and reveal an important additional source of specificity in the aminoacylation reaction. Crystal structures of the GlnRS x tRNA complex bound to either amino acid have previously shown that glutamine and glutamate bind in distinct positions in the active site, providing a structural basis for the amino acid-dependent modulation of tRNA affinity. Together with other crystallographic data showing that ligand binding is essential to assembly of the GlnRS active site, these findings suggest a model for specificity generation in which required induced-fit rearrangements are significantly modulated by the identities of the bound substrates.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

POVEZANOST RADA