Eukaryotic polypeptide chain release factor eRF3 is an eRF1- and ribosome-dependent guanosine triphosphatase.
Termination of translation in eukaryotes is governed by two polypeptide chain release factors, eRF1 and eRF3 on the ribosome. eRF1 promotes stop-codon-dependent hydrolysis of peptidyl-tRNA, and eRF3 interacts with eRF1 and stimulates eRF1 activity in the presence of GTP. Here, we have demonstrated that eRF3 is a GTP-binding protein endowed with a negligible, if any, intrinsic GTPase activity that is profoundly stimulated by the joint action of eRF1 and the ribosome. Separately, neither eRF1 nor the ribosome display this effect. Thus, eRF3 functions as a GTPase in the quaternary complex with ribosome, eRF1, and GTP. From the in vitro uncoupling of the peptidyl-tRNA and GTP hydrolyses achieved in this work, we conclude that in ribosomes both hydrolytic reactions are mediated by the formation of the ternary eRF1-eRF3-GTP complex. eRF1 and the ribosome form a composite GTPase-activating protein (GAP) as described for other G proteins. A dual role for the revealed GTPase complex is proposed: in " GTP state," it controls the positioning of eRF1 toward stop codon and peptidyl-tRNA, whereas in "GDP state," it promotes release of eRFs from the ribosome. The initiation, elongation, and termination steps of protein synthesis seem to be similar with respect to GTPase cycles.
Frolova
L
L
Département de Biologie et Génétique du Développement, CNRS URA 256, Université de Rennes 1, France.
Le Goff
X
X
Zhouravleva
G
G
Davydova
E
E
Philippe
M
M
Kisselev
L
L
D001483:Base Sequence; D017931:DNA Primers; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism; D008969:Molecular Sequence Data; D010443:Peptide Chain Termination, Translational; D010454:Peptide Termination Factors / Q000378:metabolism*; D011485:Protein Binding; D012270:Ribosomes / Q000378:metabolism*
D017931:DNA Primers; D010454:Peptide Termination Factors; C087971:peptide-chain-release factor 3; D006160:Guanosine Triphosphate; D020558:GTP Phosphohydrolases