Naslov
Defining the active site of yeast seryl-tRNA synthetase

Autori
Lenhard, Boris ; Filipić, Sanda ; Landeka, Irena ; Škrtić, Ivan ; Soll, Dieter ; Weygand-Đurašević, Ivana

Izvornik
The Journal of biological chemistry (0021-9258) 272 (1997), 2; 1136-1141

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

Ključne riječi
aminoacyl-tRNA synthetase; seryl-tRNA; mutagenesis; Saccharomyces cerevisiae

Sažetak
The active site of class II aminoacyl-tRNA synthetases contains the motif 2 loop, which is involved in binding of ATP, amino acid, and the acceptor end of tRNA. In order to characterize the active site of Saccharomyces cerevisiae seryl-tRNA synthetase (SerRS), we performed in vitro mutagenesis of the portion of the SES1 gene encoding the motif 2 loop. Substitutions of amino acids conserved in the motif 2 loop of seryl-tRNA synthetases from other sources led to loss of complementation of a yeast SES1 null allele strain by the mutant yeast SES1 genes. Steady-state kinetic analyses of the purified mutant SerRS proteins revealed elevated K_m values for serine and ATP, accompanied by decreases in k_cat (as expected for replacement of residues involved in aminoacyl-adenylate formation). The differences in the affinities for serine and ATP, in the absence and presence of tRNA are consistent with the proposed conformational changes induced by positioning the 3"-end of tRNA into the active site, as observed recently in structural studies of Thermus thermophilus SerRS (Cusack, S., Yaremchuk, A., and Tukalo, M. (1996) EMBO J. 15, 2834-2842). The crystal structure of this moderately homologous prokaryotic counterpart of the yeast enzyme allowed us to produce a model of the yeast SerRS structure and to place the mutations in a structural context. In conjunction with structural data for T. termophilus SerRS, the kinetic data presented here suggest that yeast seryl-tRNA synthetase displays tRNA-dependent amino acid recognition.

Izvorni jezik
Engleski

Znanstvena područja
Kemija, Biologija

POVEZANOST RADA