ABSTRACT
A conserved protein translocation channel is form ed by the hetero-trimeric Sec61 complex in eucaryotes and by SecY complex in archaea and eubacteria. Experimental observations including biochemical, biophysical and electron microscopy studies indicate that oligomers o f the hetero-trimeric Sec61 /SecY complexes form the channel through the membrane. Nevertheless, the determined crystallographic high resolution structure o f an archaeal SecY complex indicates that the pore may be located at the center o f a single hetero-trimeric complex. Based on this structure molecular models were developed to envisage how secretory proteins are transported across the membrane and how lateral insertion o f transmembrane segments into the lipid bilayer may occur.
