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  • The EMBO Journal (1998) 17, 3631 - 3639
  • doi:10.1093/emboj/17.13.3631



There is a Corrigendum (September 1998) associated with this Article.

PrlA4 prevents the rejection of signal sequence defective preproteins by stabilizing the SecA–SecY interaction during the initiation of translocation

Jeroen P.W. van der Wolk1,3, Peter Fekkes1,3, Andre Boorsma1, Janet L. Huie2, Thomas J. Silhavy2 and Arnold J.M. Driessen1

  1. Department of Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Kerklaan 30, 9751 NN Haren, The Netherlands
  2. Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
  3. J.P.W.van der Wolk and P.Fekkes contributed equally to this work

Correspondence to:

Arnold J.M. Driessen, E-mail: A.J.M.Driessen@BIOL.RUG.NL

Received 19 February 1998; Accepted 8 May 1998; Revised 8 May 1998

In Escherichia coli, precursor proteins are translocated across the cytoplasmic membrane by translocase. This multisubunit enzyme consists of a preprotein-binding and ATPase domain, SecA, and the SecYEG complex as the integral membrane domain. PrlA4 is a mutant of SecY that enables the translocation of preproteins with a defective, or missing, signal sequence. Inner membranes of the prlA4 strain efficiently translocate Delta8proOmpA, a proOmpA derivative with a non-functional signal sequence. Owing to the signal sequence mutation, Delta8proOmpA binds to the translocase with a lowered affinity and the recognition is not restored by the prlA4 SecY. At the ATP-dependent initiation of translocation, the binding affinity of SecA for SecYEG is lowered causing the premature loss of bound preproteins from the translocase. The prlA4 membranes, however, bind SecA with a much higher affinity than the wild-type, and during initiation, the SecA and preprotein remain bound at the translocation site allowing an improved efficiency of translocation. It is concluded that the prlA4 strain prevents the rejection of defective preproteins from the export pathway by stabilizing SecA at the SecYEG complex.

  • Keywords:

    • proof-reading,
    • SecA,
    • SecY,
    • signal sequence