S. Panzner et al., POSTTRANSLATIONAL PROTEIN-TRANSPORT IN YEAST RECONSTITUTED WITH A PURIFIED COMPLEX OF SEC PROTEINS AND KAR2P, Cell, 81(4), 1995, pp. 561-570
We have reproduced the posttranslational mode of protein translocation
across the endoplasmic reticulum membrane with reconstituted proteoli
posomes containing a purified complex of seven yeast proteins. This Se
c complex includes a heterotrimeric Sec61p complex, homologous to that
in mammals, as well as all other membrane proteins found in genetic s
creens for translocation components. Efficient posttranslational trans
location also requires the addition of lumenal Kar2p (BiP) and ATP. Th
e trimeric Sec61p complex also exists as a separate entity that, in co
ntrast with the large Sec complex, is associated with membrane-bound r
ibosomes. We therefore hypothesize that distinct membrane protein comp
lexes function in co- and posttranslational translocation pathways.