The signal recognition particle targeting pathway does not necessarily deliver proteins to the Sec-translocase in Escherichia coli.

S. Cristobal, P.A. Scotti, S. Luirink, G. von Heyne, J.-W. de Gier

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Abstract

Prow is an Escherichia coli inner membrane protein that consists of a 100-residue-long periplasmic N-terminal tail (N-tail) followed by seven closely spaced transmembrane segments. N-tail translocation presumably proceeds in a C-to-N-terminal direction and represents a poorly understood aspect of membrane protein biogenesis. Here, using an in vivo depletion approach, we show that N-tail translocation in a ProW derivative comprising the N-tail and the first transmembrane segment fused to the globular P2 domain of leader peptidase depends both on the bacterial signal recognition particle (SRP) and the Sec-translocase. Surprisingly, however, a deletion construct with only one transmembrane segment downstream of the N-tail can assemble properly even under severe depletion of SecE, a central component of the Sec-translocase, but not under SRP-depletion conditions. To our knowledge, this is the first demonstration that the SRP-targeting pathway does not necessarily deliver SRP-dependent inner membrane proteins to the Sec-translocase. The data further suggest that N-tail translocation can proceed in the absence of a functional Sec-translocase.
Original languageEnglish
Pages (from-to)20068-20070
Number of pages3
JournalJournal of Biological Chemistry
Volume274
DOIs
Publication statusPublished - 1999

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