Department of Agricultural Chemistry, University of Tokyo, Japan.
The host-vector systems of an n-alkane-assimilating-yeast, Candida maltosa, that we previously constructed consisted of a vector replicating with an ARS region of this yeast, and C. maltosa strains J288 (leu2) or CH1 (his5) as hosts. Since each of these hosts has a single genetic marker, we have developed a new host-vector system using two genetic markers. By UV irradiation of strain CH1, an adenine auxotrophic mutant, CHA1, forming red colonies was isolated. A DNA fragment complementing this deficiency was isolated from the C. maltosa genome. Since the DNA fragment also complemented the ade1 mutation of S. cerevisiae, we termed a gene contained in this DNA fragment C-ADE1. The nucleotides of C-ADE1 were sequenced. The deduced amino acid sequence (291 residues) had 65.6% homology with that of ADE1 of S. cerevisiae (306 residues). Having the cloned C-ADE1 DNA, we improved the host-vector system of C. maltosa.