Direct visualization of conformations and conformational dynamics of the proton-driven translocation factor SecDF in supported lipid bilayers

Abstract

The general secretory, or Sec, system is a primary method of exporting proteins from the cytosol of Escherichia coli and all eubacteria. Integral membrane protein complex SecDF is a translocation factor that enhances the polypeptide secretion process that is driven by the Sec translocase, consisting of translocon SecYEG and ATPase SecA. Studies have suggested that SecDF utilizes a proton gradient to undergo cycles of conformational changes to effectively pull polypeptide species into the periplasm, independent of the ATP hydrolysis performed by SecA.