Molecular cloning, characterization and localization of PfPK4, an eIF-2alpha kinase-related enzyme from the malarial parasite Plasmodium falciparum.

PfPK4, a protein kinase gene from the human malarial parasite Plasmodium falciparum, has been cloned utilizing oligonucleotide probing. The gene encodes a protein of a predicted length of 1123 amino acids, and within this amino acid sequence all the conserved regions characteristic of protein kinases can be identified. The catalytic kinase domain possesses highest identities (34‐37%) with eukaryotic initiation factor-2a (eIF-2a) kinases, especially haem-regulated inhibitory (HRI) protein kinases. There are two kinase inserts in PfPK4, located at positions common to eIF-2a kinases. The first insert separates kinase subdomains IV and VI by 559 amino acids, and the second subdomains VII and VIII by 41 amino acids. Both inserts are larger than their homologues in eIF-2a kinases. The sequence of PfPK4 has one putative haemin-binding site. The recombinant protein, expressed in Escherichia coli, phosphorylates a synthetic peptide representing a substrate of eIF-2a kinases. Autophosphorylation