SUMMARY PARAGRAPH for SPC3
SPC3 encodes a subunit of the signal peptidase complex (SPC), which cleaves the signal sequence from proteins targeted to the endoplasmic reticulum (ER) (1, 2). 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 3 and 4.
The yeast SPC comprises four proteins, Spc1p, Spc2p, Spc3p, and Sec11p (5, 6). Spc3p is homologous to the mammalian signal peptidase subunit SPC22/23 (1, 2). SPC3 is essential for viability and for signal peptidase activity (1, 2). Depletion of Spc3p causes loss of signal peptidase activity and reduces levels of the other SPC proteins (2). Overexpression of SPC3 suppresses a temperature-sensitive mutation in SEC11, which encodes the catalytic SPC subunit (1), and Spc3p and Sec11p can be coimmunoprecipitated (7).
Last updated: 2000-12-08