Protein factors involved in the replication of sea urchin mitochondrial DNA

A mitochondrial protein of 40 kDa, able to specifically bind two double-stranded homologous sequences of mitochondrial DNA, has been purified by means of affinity chromatography from Paracentrotus lividus eggs. The binding sites are located one in the main non coding region and the other at the junction of ND5/ND6 genes, and are recognized also in a single-stranded DNA conformation. Interestingly, the 40 kDa sea urchin protein recognizes also a sequence of the human mitochondrial DNA D-loop laying between the two promoters; therefore the possibility of the existence of a human counterpart of the P.lividus protein is investigated. The developmental accumulation of the 40 KDa protein shows a decrease from egg toward pluteus stage. The features of this protein and of other DNA-binding factors characterized in Strongylocentrotus purpuratus , suggest an involvment in the regulation of sea urchin mitochondrial DNA replication.