Identification, expression, modeled structure and serological characterization of Plasmodium vivax histone 2B

Histones play important role in DNA packaging, replication and gene expression. Here, we describe the isolation and characterization of histone 2B (PvH2B) gene from the most common but non-cultivable human malaria parasite Plasmodium vivax. The isolated cDNA clone of PvH2B was allowed to express in Escherichia coli and the recombinant protein was purified by affinity chromatography. The expressed PvH2B protein showed DNA-binding properties on the South-Western analysis and the confocal microscopy localized it in the parasite nucleus. This gene is actively expressed during blood stages of the parasite and all P. vivax patients produced antibodies against the protein. The mRNA of PvH2B was found to contain a poly(A) tail at its 3' end, unlike abundant mRNA of human H2B. The encoded polypeptide is 118 amino acid long contains a nuclear targeting site, a signature motif of H2B and showed 74% homology to its host molecule. The structure of PvH2B showed that it has certain differences from that of its host at critical functional sites (viz acetylation, methylation, trypsin cleavage, DNA-binding and inter-histone interaction) which are required for general gene expression and DNA packaging. The distinctive structural features of P. vivax H2B described here may help in designing the specific antimalarial drugs.