Identification of a putative response regulator two-component phosphorelaygene (CaSSK1) from Candida albicans

We have identified and analysed a putative response regulator two-component gene (CaSSK1) from Candida albicans and its encoding protein (CaSsk1p). Ca SSK1 has an open reading frame of 2022 bp. In the promotor region of CaSSK1 a short sequence is found that matches the consensus sequence of the stres s response elements (STRE) from Saccharomyces cerevisiae. CaSSK1 is located on chromosome 1 and is expressed in either yeast or mycelial phases of C. albicans. CaSSK1 encodes a 674 amino acid protein (CaSsk1p) with an estimat ed molecular mass of 73.5 kDa and a basic isoelectric point (pI 9.5). It ha s a tripeptide (NKA) located in its C-terminus, which resembles the peroxis omal signalling target type 1 sequence (PST1) of most of the peroxisomal ma trix proteins. A homology search of CaSsk1p with other proteins in database s showed that the C-terminus of CaSsk1p exhibits the greatest similarity wi th the C-terminus of Ssk1p and Mcs4 from Saccharomyces cerevisiae and Schiz osaccharomyces pombe, respectively. The response regulator domain of CaSsk1 p contains the motifs that are characteristic of all response regulators, i ncluding the conserved aspartate and lysine residues as well as the putativ e aspartate, which is phosphorylated by a phosphohistidine residue. Finally , in spite of the structural similarities among CaSsk1p, Ssk1p and Mcs4, Ca Ssk1p does not seem to exhibit functional homology with these proteins. The Accession No. for the described sequence is AF084608, as filed in the EMBL /GenBank/DDBJ database. Copyright (C) 1999 John Wiley & Sons, Ltd.