Fidelity, mismatch extension, and proofreading measurements of apPOL, the Plasmodium falciparum apicoplast-targeted DNA polymerase

Malaria is one of the most common infectious diseases found in developing and tropical regions of the world. It is contracted over 200 million times annually, almost 800,000 of which are fatal. The primary causative agent of malaria is Plasmodium falciparum, a parasite of the phylum Apicomplexa, members of which are characterized by an essential non-photosynthetic organelle called the apicoplast. Like the chloroplast and mitochondria, the apicoplast contains its own genome, which needs to be properly replicated with each cell division for continued survival. To date, the gene PfPREX, a novel polyprotein, encodes for the only known helicase, primase, and polymerase involved in replication of the genome of the apicoplast. In this investigation we characterized the fidelity of the DNA polymerase (apPOL) and examined its ability to extend or remove various base-paring mismatches. This allowed us to determine the relative likelihood of each misincorporation. The purpose of these investigations is to better understand apPOL, which is a vital part of the machinery of Plasmodium falciparum as well as a unique polymerase itself. While the other two products of PfPREX have been shown to be related to those of T7 bacteriophage, the most similar polymerase to apPOL is that of DNA polymerase I of Aquifex aeolicus, a thermophilic bacteria. It is also part of a small group of polymerases that are related to but distinct from prototypical A-family DNA polymerases. For these reasons we have chosen to investigate this important DNA polymerase