Evolutionary conservation of components of the protein translocation complex

Publisher Website
Google Scholar
Abstract
Protein translocation into the mammalian endoplasmic reticulum requires the Sec61p complex, which consists of three membrane proteins. The alpha-subunit, the homologue of Sec61p of yeast, shows some similarity to SecYp, a key component of the protein export apparatus of bacteria. In Escherichia coli, SecYp is also associated with two other proteins (SecEp and band-1 protein). We have now determined the sequences of the beta- and gamma-subunits of the mammalian Sec61p complex. Sec61-gamma is homologous to SSS1p, a suppressor of sec61 mutants in Saccharomyces cerevisiae, and can functionally replace it in yeast cells. Moreover, Sec61-gamma and SSS1p are structurally related to SecEp of E. coli and to putative homologues in various other bacteria. At least two subunits of the Sec61/SecYp complex therefore seem to be key components of the protein translocation apparatus in all classes of organisms.