Tuyển tập các báo cáo nghiên cứu về sinh học được đăng trên tạp chí sinh học Journal of Biology đề tài: Movement in ribosome translocation. | J. Biol. Journal of Biology BioMed Central Minireview Movement in ribosome translocation Christopher S Fraser and John WB Hersheyt Addresses Department of Molecular and Cell Biology Howard Hughes Medical Institute University of California Berkeley CA 947020 USA. Department of Biochemistry and Molecular Medicine School of Medicine University of California Davis CA 95616 USA. Correspondence John WB Hershey. E-mail jwhershey@ Published 27 June 2005 Journal of Biology 2005 4 8 The electronic version of this article is the complete one and can be found online at http content 4 2 8 2005 BioMed Central Ltd Abstract Translocation of peptidyl-tRNA and mRNA within the ribosome during protein synthesis is promoted by the elongation factor EF-G and by the hydrolysis of GTP. A new study reports that EF-G binds to ribosomes as an EF-G GDP complex and that GTP is exchanged for GDP on the ribosome. Together with cryo-electron microscopy this unexpected finding helps clarify the role of GTP in translocation. Small GTPases play central roles in catalyzing each stage of protein synthesis on the ribosome. In prokaryotes the relevant GTPases are initiation factor IF2 which delivers the initiator tRNA to the P peptide site of the 30S ribosomal subunit elongation factor EF-Tu which delivers the aminoacyl-tRNA to the 70S ribosome composed of 50S and 30S subunits elongation factor EF-G which promotes the translocation of tRNAs and the mRNA within the ribosome and peptide release factor RF3 which promotes the dissociation of the release factors RF1 and RF2 following peptide release. These factors have been assumed to resemble classical GTPases with the active form of the protein being the GTP binary complex. For example the active EF-Tu GTP complex binds aminoacyl-tRNA and transports it to the ribosome which then stimulates the GTPase activity of EF-Tu functioning as a GTPase-activator protein or GAP upon detection of a correct codon-anticodon interaction 1 . Following
