How initiation factors maximize the accuracy of tRNA selection in initiation of bacterial protein synthesis.
During initiation of bacterial protein synthesis, messenger RNA and fMet-tRNAfMet bind to the 30S ribosomal subunit together with initiation factors IF1, IF2, and IF3. Docking of the 30S preinitiation complex to the 50S ribosomal subunit results in a peptidyl-transfer competent 70S ribosome. Initiation with an elongator tRNA may lead to frameshift and an aberrant N-terminal sequence in the nascent protein. We show how the occurrence of initiation errors is minimized by (1) recognition of the formyl group by the synergistic action of IF2 and IF1, (2) uniform destabilization of the binding of all tRNAs to the 30S subunit by IF3, and (3) an optimal distance between the Shine-Dalgarno sequence and the initiator codon. We suggest why IF1 is essential for E. coli, discuss the role of the G-C base pairs in the anticodon stem of some tRNAs, and clarify gene expression changes with varying IF3 concentration in the living cell.
Antoun
Ayman
A
Department of Cell and Molecular Biology, Biomedical Centre, Uppsala University, S-751 24 Uppsala, Sweden.
Pavlov
Michael Y
MY
Lovmar
Martin
M
Ehrenberg
Måns
M
D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000235:genetics; D001667:Binding, Competitive; D007700:Kinetics; D008954:Models, Biological; D039861:Prokaryotic Initiation Factor-1 / Q000502:physiology; D039881:Prokaryotic Initiation Factor-2 / Q000502:physiology; D039665:Prokaryotic Initiation Factor-3 / Q000502:physiology; D039662:Prokaryotic Initiation Factors / Q000145:classification / Q000502:physiology*; D014176:Protein Biosynthesis; D012358:RNA, Transfer, Met / Q000235:genetics / Q000378:metabolism*; D012360:RNA, Transfer, Phe / Q000235:genetics / Q000378:metabolism*; D012269:Ribosomal Proteins / Q000378:metabolism*
D001426:Bacterial Proteins; D039861:Prokaryotic Initiation Factor-1; D039881:Prokaryotic Initiation Factor-2; D039665:Prokaryotic Initiation Factor-3; D039662:Prokaryotic Initiation Factors; D012358:RNA, Transfer, Met; D012360:RNA, Transfer, Phe; D012269:Ribosomal Proteins; C040469:ribosomal protein S30