Molecular cloning and localization of an abundant novel protein of Plasmodium berghei

Screening of Plasmodium berghei genomic libraries using DNA insert corresponding to the 3′ half of P. falciparum 70-kDa heat shock protein gene identified several abundant clones which represent a novel gene in the parasite. The complete sequence was obtained using an approach based on inverse polymerase chain reaction. Analysis of the deduced amino acid sequence revealed the presence of 19 imperfect repeats of the sequence Gly-Gly-Met-Pro toward the carboxy terminus. Except for the similar sequence repeated seven times in the malarial 70-kDa heat shock protein, the sequence of the cloned gene product is very different. Moreover, the sequence also revealed acidic and basic domains in the protein which are more than 60% similar in sequence to functional domains present in numerous DNA binding transcription factors. A 56-kDa protein was identified by immunoprecipitation from labeled P. berghei extract using antisera raised in mice against gene products expressed in Escherichia coli. The protein is present in all the different life cycle stages of the parasites as revealed by immuno-electron microscopy.