SUMMARY PARAGRAPH for SEC11
SEC11 encodes the catalytic subunit of the signal peptidase complex (SPC), which cleaves the signal sequence from proteins targeted to the endoplasmic reticulum (ER) (2, 3). Signal peptide cleavage occurs concomitantly with translocation through the translocon pore into the ER. In yeast, translocation can occur cotranslationally or posttranslationally, whereas in mammals translocation is always cotranslational. The process of protein translocation into the ER is reviewed in references 5 and 6.
The yeast SPC comprises four proteins, Spc1p, Spc2p, Spc3p, and Sec11p (3, 7). SEC11 is essential for viability and for signal peptidase activity (2). SEC11 interacts genetically with the genes encoding the other SPC subunits (8, 9, 10), and Sec11p can be coimmunoprecipitated with Spc3p (11).
Sec11p is homologous to the mammalian signal peptidase subunits SPC18 and SPC21 (12), and shows some sequence similarity the catalytic site of the Bacillus subtilis leader peptidase SipW (11). Indeed, Sec11p has signal peptidase catalytic activity, although the phenotypes of mutations in the putative catalytic site of Sec11p suggest that the catalytic mechanism of Sec11p differs from that of SipW (11).
Last updated: 2000-12-08