Isolation of a Histoplasma capsulatum cDNA that complements a mitochondrial NAD(+)-isocitrate dehydrogenase subunit I-deficient mutant of Saccharomyces cerevisiae.

A cDNA library was prepared from Histoplasma capsulatum strain G-217B yeast cells and an apparently full-length cDNA for a subunit of the citric acid cycle enzyme NAD(+)-isocitrate dehydrogenase was identified by sequence analysis. Its predicted amino acid sequence is more similar to the IDH1 regulatory subunit of S. cerevisiae NAD(+)-isocitrate dehydrogenase than to the IDH2 catalytic subunit. After expression in S. cerevisiae from an S. cerevisiae promoter, it was shown to functionally complement an S. cerevisiae idh1 mutant, but not an idh2 mutant, for growth on acetate as a carbon source and for production of NAD(+)-isocitrate dehydrogenase enzyme activity. These results confirm that the H. capsulatum cDNA encodes a homologue of subunit I of the S. cerevisiae mitochondrial isocitrate dehydrogenase isozyme that functions in the citric acid cycle.