Cloning and characterization of the lactate-specific inducible gene KICYB2, encoding the cytochrome b(2) of Kluyveromyces lactis

In yeast the utilization of lactate requires two enzymes, the D and L-actat e ferricytochrome c oxidoreductase (D and L-LCR), which stereospecifically oxidize D- and L-lactate to pyruvate. These enzymes are nuclearly encoded a nd localized in mitochondria. In the yeast Kluyveromyces lactis, a mutant d evoid of D- and L-LCR activities and unable to grow on racemic lactate was isolated. Transformation of the mutant with a K. lactis genomic library all owed the isolation of the KlCYB2 gene, restoring the growth on lactate and the L-LCR activity. The KlCYB2 gene and its flanking regions were sequenced (Accession No, AJ243324; EMBL/GenBank databases). The deduced amino acid s equence is highly homologous to the corresponding Saccharomyces cerevisiae and Hansenula anomala protein sequences previously characterized. The homol ogy is missed in the N-terminal region, corresponding to the presequence cl eaved during import into mitochondria. Analysis of KlCYB2 gene expression i ndicated that, in contrast to S. cerevisiae, the major regulatory feature i s induction by lactate. Copyright (C) 2000 John Whey & Sons, Ltd.