GENES OF THE LINEAR MITOCHONDRIAL-DNA OF WILLIOPSIS-MRAKII - CODING SEQUENCES FOR A MATURASE-LIKE PROTEIN, A RIBOSOMAL-PROTEIN VAR1 HOMOLOG, CYTOCHROME-OXIDASE SUBUNIT 2 AND METHIONYL TRANSFER-RNA

The mitochondrial DNA (mtDNA) in some yeasts has a linear structure wi th inverted terminal repeats closed by a single-stranded loop. These m tDNAs have generally a constant gene order, beginning with a small rib osomal RNA gene at the right end and terminating with a cytochrome oxi dase subunit 2 gene (COX2) at the left end, independently of the wide variation in genome size. In the mtDNAs from several species of the ge nus Williopsis, we found an additional open reading frame, ORF1, which was homologous to the Saccharomyces cerevisiae RF1 gene encoding a gr oup I intron maturase-like protein. ORF1 genes from W. mrakii and W. s uaveolens were mapped and sequenced. Next to ORF1, COX2 and methionyl tRNA genes were present on the opposite strand. The same relative posi tions of genes in the mtDNAs so far examined suggests that the constan cy of gene order is generally conserved also at the level of individua l tRNA genes. We identified another open reading frame, ORF2, in W. mr akii mtDNA. It was mapped next to the cytochrome oxidase subunit 3 gen e. Rich in adenine-thymine bases, ORF2 appears to be a homologue of th e VAR1 gene which codes for a small ribosomal subunit protein in S. ce revisiae mitochondria. Nucleotide sequences data have been deposited i n the EmBL data library under the following Accession Numbers: X66594 (Apocytochrome b and ORF2 genes of W: mrakii), X66595 (ORF1, tRNA-Met and COX2 genes of W. mrakii), X73415 (tRNA-Met and COX2 genes of Wi su aveolens), X73416 (ORF1 gene of W. suaveolens) and X73414 (tRNA-Met an d COX2 genes of P. jadinii).