Synergistic insertion of two hydrophobic regions drives Sec-independent membrane protein assembly

Guoqing Cao, Shiyuan Cheng, Paul Whitley, Gunnar Von Heijne, Andreas Kuhn, Ross E. Dalbey*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

27 Scopus citations


We have studied the membrane insertion of two proteins from the inner membrane of Escherichia coli, both with two transmembrane segments connected by a short periplasmic loop: the M13 procoat protein and a mutant 'inverted' leader peptidase. Neither molecule depends on the Sec machinery for insertion. We show that the introduction of a charged residue in the second transmembrane segment completely blocks insertion of both proteins. In contrast, a Sec-dependent procoat mutant, where the periplasmic region has been lengthened, inserts into the membrane even in the presence of a charged residue in the second hydrophobic domain. In addition, a large deletion within the second transmembrane domain of the leader peptidase mutant allows membrane translocation, but only under conditions where the SecA protein is functional. Furthermore, we show that the first hydrophobic domain is required for insertion of the short periplasmic loop of the 'inverted' leader peptidase. These results suggest that Sec-independent insertion occurs by a synergistic entry of the two neighboring hydrophobic domains into the lipid bilayer.

Original languageEnglish (US)
Pages (from-to)26898-26903
Number of pages6
JournalJournal of Biological Chemistry
Issue number43
StatePublished - Oct 28 1994

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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