Plasmodium falciparum, the major causative agent of human malaria, contains 
three separate genomes. The apicoplast (an intracellular organelle) contains an 
∼35-kb circular DNA genome of unusually high A/T content (>86%) that is 
replicated by the nuclear-encoded replication complex Pfprex. Herein, we have 
expressed and purified the DNA polymerase domain of Pfprex [KPom1 (Klenow-like 
polymerase of malaria 1)] and measured its fidelity using a LacZ-based forward 
mutation assay. In addition, we analyzed the kinetic parameters for the 
incorporation of both complementary and noncomplementary nucleotides using Kpom1 
lacking 3'→5' exonucleolytic activity. KPom1 exhibits a strongly biased 
mutational spectrum in which T→C is the most frequent single-base substitution 
and differs significantly from the closely related Escherichia coli DNA 
polymerase I. Using E. coli harboring a temperature-sensitive polymerase I 
allele, we established that KPom1 can complement the growth-defective phenotype 
at an elevated temperature. We propose that the error bias of KPom1 may be 
exploited in the complementation assay to identify nucleoside analogs that mimic 
this base-mispairing and preferentially inhibit apicoplast DNA replication.