Comparative kinomics of Plasmodium organisms: unity in diversity

Phosphorylation by protein kinases is a very common and crucial process in many signal transduction pathways in eukaryotes. This review describes comparative protein kinase analysis of two apicomplexa Plasmodium falciparum (3D7 strain) and Plasmodium yoelii yoelii (17XNL strain) which are causative agents of malaria in human and African rat respectively. Sensitive bioinformatics techniques enable identification of 82 and 60 putative protein kinases in P. falciparum and P. yoelii yoelii respectively and these sequences could be classified into known subfamilies of protein kinases. The most populated kinase subfamilies in both the plasmodium species correspond to CAMK and CMGC groups. Analysis of domain architectures enables detection of uncommon domain organization in kinases of both the organisms such as kinase domain tethered to EF hands as well as PH domain. Components of MAPK signaling pathway is not well conserved in plasmodium organisms. Such observations suggest that plasmodium protein kinases are highly divergent from other eukaryotes. A transmembrane kinase with 6 membrane spanning segments in P. falciparum seems to have no orthologue in P. yoelii yoelii. 19 P. falciparum kinases have been found to cluster separately from P. yoelii yoelii kinases and hence these kinases are unique to P. falciparum genome. Only 28 orthologous pairs of kinases seem to be present between these two plasmodium organisms. Comparative kinome analysis of two plasmodium species has thus provided clues to the function of many protein kinases based upon their classification and domain organization and also implicate marked differences even between two plasmodium organisms.