Characterization of Candida albicans orthologue of the Saccharomyces cerevisiae signal‐peptidase‐subunit encoding gene SPC3

The Candida albicans orthologue of the SPC3 gene, which encodes one of the subunits essential for the activity of the signal peptidase complex in Saccharomyces cerevisiae , was isolated by complementation of a thermosensitive mutation in the S. cerevisiae SEC61 gene. The cloned gene ( CaSPC3 ) encodes a putative protein of 192 amino acids that contains one potential membrane‐spanning region and shares significant homology with the corresponding products from mammalian (Spc22/23p) and yeast (Spc3p) cells. CaSPC3 is essential for cell viability, since a hemizygous strain containing a single copy of CaSPC3 under control of the methionine‐repressible MET3 promoter did not grow in the presence of methionine and cysteine. The cloned gene could rescue the phenotype associated with a spc3 mutation in S. cerevisiae , indicating that it is the true C. albicans orthologue of SPC3 . However, in contrast with results previously described for its S. cerevisiae orthologue, CaSPC3 was not able to complement the thermosensitive growth associated with a mutation in the SEC11 gene. The heterologous complementation of the sec61 mutant suggests that Spc3p could play a role in the interaction that it is known to occur between the translocon (Sec61 complex) and the signal peptidase complex, at the endoplasmic reticulum membrane. Copyright © 2004 John Wiley & Sons, Ltd.