title: Interaction of RRF and EF-G from E. coli and T. thermophilus with ribosomes from both origins--insight into the mechanism of the ribosome recycling step.
abstract: Ribosome recycling factor (RRF), elongation factor-G (EF-G), and ribosomes from Thermus thermophilus (tt-) and Escherichia coli (ec-) were used to study the disassembly mechanism of post-termination ribosomal complexes by these factors. With tt-RRF, ec-EF-G can release bound-tRNA from ec-model post-termination complexes. However, tt-RRF is not released by ec-EF-G from ec-ribosomes. This complex with tt-RRF and ec-ribosomes after the tRNA release by ec-EF-G is regarded as an intermediate of the disassembly reaction. Not only tt-RRF, but also mRNA, cannot be released from ec-ribosomes by tt-RRF and ec-EF-G. These data suggest that the release of RRF from ribosomes is coupled or closely related to the release of mRNA during disassembly of post-termination complexes. With tt-ribosomes, ec-EF-G cannot release ribosome-bound ec-RRF even though they are from the same species, showing that proper interaction of ec-RRF and ec-EF-G does not occur on tt-ribosomes. On the other hand, in contrast to a published report, tt-EF-G functions with ec-RRF to disassemble ec-post-termination complexes. In support of this finding, tt-EF-G translocates peptidyl tRNA on ec-ribosomes and catalyzes ec-ribosome-dependent GTPase, showing that tt-EF-G has in vitro translocation activity with ec-ribosomes. Since tt-EF-G with ec-RRF can release tRNA from ec-post-termination complexes, the data are consistent with the hypothesis that the release of tRNA by RRF and EF-G from post-termination complexes is a result of a translocation-like activity of EF-G on RRF.
authors.affiliation: Department of Microbiology, School of Medicine, University of Pennsylvania, Room 203B, Johnson Pavilion, 3610 Hamilton Walk, Philadelphia, PA 19104, USA.
authors.forename: V Samuel
authors.initials: VS
authors.lastname: Raj
authors.forename: Hideko
authors.initials: H
authors.lastname: Kaji
authors.forename: Akira
authors.initials: A
authors.lastname: Kaji
mesh_terms: D001483:Base Sequence; D002384:Catalysis; D017931:DNA Primers; D004926:Escherichia coli / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism; D006868:Hydrolysis; D020653:Peptide Elongation Factor G / Q000378:metabolism*; D011485:Protein Binding; D011506:Proteins / Q000378:metabolism*; D012269:Ribosomal Proteins; D012270:Ribosomes / Q000378:metabolism*; D016963:Thermus thermophilus / Q000378:metabolism*
chemical_list: D017931:DNA Primers; D020653:Peptide Elongation Factor G; D011506:Proteins; D012269:Ribosomal Proteins; C087267:ribosome releasing factor; D006160:Guanosine Triphosphate