The bacterial SecY/E translocation complex forms channel-like structures similar to those of the eukaryotic Sec61p complex

The SecYEG complex is a major component of the protein translocation appara tus in the cytoplasmic membrane of bacteria. We have purified a translocati onally active complex of the two subunits, SecY and SecE, from Bacillus sub tilis. As demonstrated by electron microscopy, SecY/E forms ring structures in detergent solution and in intact lipid bilayers, often with a quasi-pen tagonal appearance in projection. The particles represent oligomeric assemb lies of the SecY/E complex and are similar to those formed by the eukaryoti c Sec61p complex. We propose that these SecY/E rings represent protein-cond ucting channels and that the two essential membrane components SecY and Sec E are sufficient for their formation. (C) 1999 Academic Press.