Complete nucleotide sequence of the 6 kb element and conserved cytochrome b gene sequences among Indian isolates of Plasmodium falciparum

The malaria parasite contains a nuclear genome with 14 chromosomes and two extrachromosomal DNA molecules of 6 kb and 35 kb in size. The smallest geno me, known as the 6 kb element or mitochondrial DNA, has been sequenced from several Plasmodium falciparum isolates because this is a potential drug ta rget. Here we describe the complete nucleotide sequence of this element fro m an Indian isolate of P. falciparum. It is 5967 bp in size and shows 99.6% homology with the 6 kb element of other isolates. The element contains thr ee open reading frames for mitochondrial proteins-cytochrome oxidase subuni t I (CoI), subunit III (CoIII) and cytochrome b (Cyb) which were found to b e expressed during blood stages of the parasite. We have also sequenced the entire cyb gene from several Indian isolates of P. falciparum. The rate of mutation in this gene was very low since 12 of 14 isolates showed the iden tical sequence. Only one isolate showed a maximum change in five amino acid s whereas the other isolate showed only one amino acid change. However, non e of the Indian isolates showed any change in those amino acids of cyb whic h are associated with resistance to various drugs as these drugs are not ye t commonly used in India. (C) 2001 Australian Society for Parasitology Inc. Published by Elsevier Science Ltd. All rights reserved.