Identification of a putative mitochondrial telomere-binding protein of the yeast Candida parapsilosis

Terminal segments (telomeres) of linear mitochondrial DNA (mtDNA) molecules of the yeast Candida parapsilosis consist of large sequence units repeated in tandem. The extreme ends of mtDNA terminate with a 5' single-stranded overhang of about 110 nucleotides. We identified and purified a mitochondrial telomere-binding protein (mtTBP) that specifically recognizes a synthetic oligonucleotide derived from the extreme end of this linear mtDNA. MtTBP is highly resistant to protease and heat treatments, and it protects the telomeric probe from degradation by various DNA-modifying enzymes. Resistance of the complex to bacterial alkaline phosphatase suggests that mtTBP binds the very end of the molecule. We purified mtTBP to near homogeneity using DNA affinity chromatography based on the telomeric oligonucleotide covalently bound to Sepharose. Sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis of the purified fractions revealed the presence of a protein with an apparent molecular mass of approximately 15 kDa. UV cross-linking and gel filtration chromatography experiments suggested that native mtTBP is probably a homo-oligomer. MtTBP of C. parapsilosis is the first identified protein that specifically binds to telomeres of linear mitochondrial DNA.