Mitochondrial telomere-binding protein from Candida parapsilosis suggests an evolutionary adaptation of a nonspecific single-stranded DNA-binding protein

The mitochondrial genome in a number of organisms is represented by linear DNA molecules with defined terminal structures. The telomeres of linear mit ochondrial DNA (mtDNA) of yeast Candida parapsilosis consist of tandem arra ys of large repetitive units possessing single-stranded 5' extension of abo ut 110 nucleotides. Recently we identified the first mitochondrial telomere -binding protein (mtTBP) that specifically binds a sequence derived from th e extreme end of C, parapsilosis linear mtDNA and protects it from attack, by various DNA-modifying enzymes (Tomaska, L',, Nosek, J,, and Fukuhara, H, (1997) J, Biol, Chem, 272, 3049-3059). Here we report the isolation of MTP 1, the gene encoding mtTBP of C. parapsilosis, Sequence analysis revealed t hat mtTBP shares homology with several bacterial and mitochondrial single-s tranded DNA-binding proteins that nonspecifically bind to single-stranded D NA with high affinity, Recombinant mtTBP displays a preference for the telo meric 5' overhang of C, parapsilosis mtDNA. The heterologous expression of a mtTBP-GFP fusion protein resulted in its localization to the mitochondria but was unable to functionally substitute for the loss of the S. cerevisia e homologue Rimlp, Analysis of the MTP1 gene and its translation product mt TBP may provide an insight into the evolutionary origin of linear mitochond rial genomes and the role it plays in their replication and maintenance.