DNA-HELICASE ACTIVITY FROM SEA-URCHIN MITOCHONDRIA

As a step toward the characterization of the main components of mitoch ondrial DNA replication apparatus in sea urchin, we report the identif ication of a DNA-helicase activity in Paracentrotus lividus mitochondr ia. The activity was detected in a protein fraction obtained by fracti onating on DEAE-Sephacel a lysate of gradient purified mitochondria fr om Paracentrotus lividus eggs. The mitochondrial helicase unwound, in the presence of ATP and Mg++, a 39-base oligonucleotide annealed to si ngle-stranded M12mp18 (+) DNA. Its direction of movement is 3' to 5' w ith respect to the single stranded portion of the partial duplex DNA s ubstrate. This polarity is similar to that exhibited by the Escherichi a coli rep helicase and by the helicase from bovine brain mitochondria . These features suggest that the sea urchin mitochondrial helicase co uld function in enabling the polymerization of the H-strand during mit ochondrial DNA replication. (C) 1996 Academic Press, Inc.