The binding cascade of SecB to SecA to SecY/E mediates preprotein targeting to the E. coli plasma membrane

Cell. 1990 Oct 19;63(2):269-79. doi: 10.1016/0092-8674(90)90160-g.


The export of many E. coli proteins such as proOmpA requires the cytosolic chaperone SecB and the membrane-bound preprotein translocase. Translocase is a multisubunit enzyme with the SecA protein as its peripheral membrane domain and the SecY/E protein as its integral domain. SecB, by binding to proOmpA in the cytosol, prevents its aggregation or association with membranes at nonproductive sites. The SecA receptor binds the proOmpA-SecB complex (Kd approximately 6 x 10(-8) M) through direct recognition of both the SecB (Kd approximately 2 x 10(-7) M) as well as the leader and mature domains of the precursor protein. SecB has a dual function in stabilizing the precursor and in passing it on to membrane-bound SecA, the next step in the pathway. SecA itself is bound to the membrane by its affinity (Kd approximately 4 x 10(-8) M) for SecY/E and for acidic lipids. The functions of SecB and SecA as a two-stage receptor system are linked by their affinity for each other.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Bacterial Outer Membrane Proteins / metabolism
  • Bacterial Proteins / metabolism*
  • Cell Membrane / metabolism*
  • Escherichia coli / genetics
  • Escherichia coli / metabolism*
  • Escherichia coli Proteins*
  • Kinetics
  • Models, Biological
  • Protein Binding
  • Protein Precursors / metabolism*
  • Protein Processing, Post-Translational*
  • SEC Translocation Channels


  • Bacterial Outer Membrane Proteins
  • Bacterial Proteins
  • Escherichia coli Proteins
  • Protein Precursors
  • SEC Translocation Channels
  • SecB protein, Bacteria
  • SecY protein, E coli
  • outer membrane protein A precursor (E coli)