PURIFICATION AND CHARACTERIZATION OF A MITOCHONDRIAL DNA-BINDING PROTEIN THAT BINDS TO DOUBLE-STRANDED AND SINGLE-STRANDED SEQUENCES OF PARACENTROTUS-LIVIDUS MITOCHONDRIAL-DNA

A mitochondrial protein, able to specifically bind two double-stranded homologous sequences of sea-urchin mitochondrial DNA, has been partia lly purified from Paracentrotus lividus eggs. This protein, present at a low concentration, is a polypeptide of 40 kDa. One of the binding s equences, located in the main non-coding region, contains the replicat ion origin of the mitochondrial DNA H-strand. By a combination of band -shift, DNase footprinting, and modification interference analyses wit h homologous and heterologous, probes we identified YCYYATCAN(A/T)RC a s the minimum sequence required for the binding. The protein also show s a single-stranded DNA-binding activity, as it is able to specificall y interact with one of the strands of the binding sites. These feature s are consistent with a function of the protein in the modulation of s ea-urchin mitochondrial DNA replication during the developmental stage s.