A new factor from Escherichia coli affects translocation of mRNA.
Reconstitution of protein synthesis from purified translation factors on ribosomes from Escherichia coli has revealed the requirement for a protein, W, that affects chain elongation and is essential to reconstitute the process (Ganoza, M. C., Cunningham, C., and Green, R. M. (1985) Proc. Natl. Acad. Sci. U.S.A. 82, 1648-1652). We report that W has no effect on initiation complex formation by 30 or 70 S ribosomes or on the association of ribosomal subunits, peptide bond synthesis, or binding Ala-tRNA, which is the second amino acid of the coat protein of the MS2 RNA virion. W has a pronounced effect on tripeptide synthesis, and is obligatory for the synthesis of the coat protein or of the hexapeptide encoded by f2am3 RNA. Extracts from a temperature-sensitive mutant of the translocase, EF-G, were purified free of the W protein and were used to score for translocation defects. W is required for binding Ser-tRNA, the third N-terminal amino acid of the MS2 or f2 RNA coat protein to ribosomes bearing fMet-Ala-tRNA, as well as for the ejection of deacyl-tRNA from ribosomes, which occurred concomitant with the binding of the Ser-tRNA. We propose that W functions by ejecting tRNAs from ribosomes in a step that precedes the movement of mRNA during translocation.
Ganoza
M C
MC
Banting and Best Department of Medical Research, University of Toronto, Ontario, Canada.
Cunningham
C
C
Green
R M
RM
D001426:Bacterial Proteins / Q000302:isolation & purification / Q000378:metabolism*; D002213:Capsid / Q000096:biosynthesis; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D020963:GTP Phosphohydrolase-Linked Elongation Factors / Q000378:metabolism; D007700:Kinetics; D017909:Levivirus / Q000378:metabolism; D020653:Peptide Elongation Factor G; D010445:Peptide Elongation Factors / Q000302:isolation & purification / Q000378:metabolism; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000378:metabolism*; D012344:RNA, Transfer, Ala / Q000378:metabolism; D012345:RNA, Transfer, Amino Acid-Specific / Q000378:metabolism*; D012362:RNA, Transfer, Ser / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism*; D014771:Virion / Q000378:metabolism
D001426:Bacterial Proteins; D020653:Peptide Elongation Factor G; D010445:Peptide Elongation Factors; D012333:RNA, Messenger; D012344:RNA, Transfer, Ala; D012345:RNA, Transfer, Amino Acid-Specific; D012362:RNA, Transfer, Ser; D020963:GTP Phosphohydrolase-Linked Elongation Factors