A Subunit of Mammalian Signal Peptidase Is Homologous to Yeast SEC11 Protein

Canine signal peptidase consists of a complex of five proteins (Evans, A. E., Gilmore, R., and Blobel, G. (1986) Proc. Natl. Acad. Sci. U. S. A. 83, 581–585). A cDNA encoding the 21-kDa subunit of the signal peptidase complex was isolated from a liver cDNA library using an 88-base pair probe, generated by the polymerase chain reaction. The 820-base pair cDNA was sequenced and found to encode a protein of 21,585 daltons. The deduced amino acid sequence from the canine cDNA was found to be 47% identical to the yeast SEC11 protein. SEC11 has been shown to be required for signal peptide cleavage, normal rate of secretion, and cell survival in Saccharomyces cerevisiae (Böhni, P. C, Deshaies, R. J., and Schekman, R. W. (1988) J. Cell Biol. 106, 1035–1042). It is, therefore, likely that the 21-kDa subunit of signal peptidase complex is the structural and functional homologue of the yeast SEC11 gene product.