A 70-kDa chloroplast DNA polymerase from pea (Pisum sativum) that shows high processivity and displays moderate fidelity

Abstract

A 70-kDa chloroplast (ct) DNA polymerase from pea has been purified to apparent homogeneity. The ct DNA polymerase was insensitive to dideoxynucleotides (d₂ NTP) but showed high sensitivity to phosphonoacetic acid. The enzyme lacked any detectable 5'→3' exonuclease activity but showed 3'→5' exonuclease activity. The polymerase displayed high processivity (3 kb) and moderate fidelity, which may be sufficient for the faithful replication of the 140-kb pea ct genome. A 43-kDa accessory protein increased the polymerization rate but did not affect the rate of mis-incorporation in vitro, thus indicating that the domains for polymerisation and proof reading may be spatially separate.