Molecular cloning of CaYRB1, the Candida albicans RanBP1/YRB1 homologue.

The yeast Ran binding protein 1 (Yrb1p) is a small protein of 23 kDa that is highly conserved among eukaryotes. It stimulates the GTPase activity of Gsp1p in the presence of the GTPase activating protein Rna1p. In addition to its role in nucleocytoplasmic transport of macromolecules, YRB1/RanBP1 could be involved in the regulation of microtubules structure and dynamics. Since microtubules are tightly associated with morphological changes, we have been interested to study the role and function of YRB1 in the pathogenic fungus Candida albicans, where there is regulated change in cellular morphology. The gene product of CaYRB1 encodes a 212 amino acid protein displaying 73% homology to the S. cerevisiae homologue. The bacterially expressed gene product has an apparent molecular weight of 35.7 kDa. We show that it can complement a S. cerevisiae yrb1 null mutant and that its mRNA does not appear to be regulated in response to conditions inducing morphological changes in C. albicans.