Qbeta-phage resistance by deletion of the coiled-coil motif in elongation factor Ts.
Elongation factor Ts (EF-Ts) is the guanine-nucleotide exchange factor of elongation factor Tu (EF-Tu), which promotes the binding of aminoacyl-tRNA to the mRNA-programmed ribosome in prokaryotes. The EF-Tu.EF-Ts complex, one of the EF-Tu complexes during protein synthesis, is also a component of RNA-dependent RNA polymerases like the polymerase from coliphage Qbeta. The present study shows that the Escherichia coli mutant GRd.tsf lacking the coiled-coil motif of EF-Ts is completely resistant to phage Qbeta and that Qbeta-polymerase complex formation is not observed. GRd.tsf is the first E. coli mutant ever described that is unable to form a Qbeta-polymerase complex while still maintaining an almost normal growth behavior. The phage resistance correlates with an observed instability of the mutant EF-Tu.EF-Ts complex in the presence of guanine nucleotides. Thus, the mutant EF-Tu.EF-Ts is the first EF-Tu.EF-Ts complex ever described that is completely inactive in the Qbeta-polymerase complex despite its almost full activity in protein synthesis. We propose that the role of EF-Ts in the Qbeta-polymerase complex is to control and trap EF-Tu in a stable conformation with affinity for RNA templates while unable to bind aminoacyl-tRNA.
Karring
Henrik
H
Department of Molecular Biology, Gustav Wieds Vej 10c, University of Aarhus, DK-8000 Aarhus C, Denmark.
Mathu
Sander G J
SG
van Duin
Jan
J
Clark
Brian F C
BF
Kraal
Barend
B
Knudsen
Charlotte R
CR
D003090:Coliphages / Q000502:physiology*; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D004926:Escherichia coli / Q000821:virology*; D029968:Escherichia coli Proteins / Q000502:physiology*; D010445:Peptide Elongation Factors / Q000737:chemistry / Q000502:physiology*; D014176:Protein Biosynthesis; D011487:Protein Conformation; D012367:RNA, Viral / Q000096:biosynthesis; D014779:Virus Replication
D029968:Escherichia coli Proteins; D010445:Peptide Elongation Factors; D012367:RNA, Viral; C023512:elongation factor Ts; D012321:DNA-Directed RNA Polymerases