Competition between ribosome and SecA binding promotes Escherichia coli secA translational regulation.
SecA protein, the protein translocation ATPase of Escherichia coli, autogenously regulates its translation during normal protein secretion by binding to a secretion-responsive element located near the 5' end of its gene on geneX-secA mRNA. In order to characterize this autoregulation further, RNA footprinting and primerextension inhibition (toeprinting) studies were carried out with a segment of geneX-secA RNA, 30S ribosomal subunits and tRNAfMet along with purified SecA protein. The results show that ribosome and SecA-binding sites overlap, indicating that a simple competition for binding of geneX-secA mRNA presumably governs the translation initiation step. Further analysis showed that SecA protein was able to specifically dissociate a preformed 30S-tRNAfMet-geneX-secA RNA ternary complex as indicated by the disappearance of its characteristic toeprint after SecA addition. These findings are consistent with secA autoregulation, and they suggest a novel mechanism for the autoregulatory behavior of this complex protein.
Salavati
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Department of Molecular Biology and Biochemistry, Wesleyan University, Middletown, Connecticut 06459, USA.
Oliver
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D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D001667:Binding, Competitive; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D026901:Membrane Transport Proteins; D008969:Molecular Sequence Data; D011485:Protein Binding; D014176:Protein Biosynthesis; D012329:RNA, Bacterial / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D012358:RNA, Transfer, Met / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism*; D000069816:SEC Translocation Channels; D000081416:SecA Proteins
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D012329:RNA, Bacterial; D012333:RNA, Messenger; D012358:RNA, Transfer, Met; D000069816:SEC Translocation Channels; D000251:Adenosine Triphosphatases; D000081416:SecA Proteins