Protein transport across the endoplasmic reticulum membrane in eukaryo
tes and across the cytoplasmic membrane in bacteria have turned out to
be highly related. The core component of the translocation apparatus
is the Sec61/SecYp complex; at least two of its subunits are conserved
in evolution. The Sec61/SecYp complex is involved in both co- and pos
t-translational transport pathways. The two modes require probably dis
tinct additional components.