Classification of Nonenzymatic Homologues of Protein Kinases

摘要

Protein Kinase-Like Non-kinases (PKLNKs), which are closely related to protein kinases,lack the crucial catalytic aspartate in the catalytic loop, and hence cannot function asprotein kinase, have been analysed. Using various sensitive sequence analysis methods, wehave recognized 82 PKLNKs from four higher eukaryotic organisms, namely,Homo sapiens,Mus musculus,Rattus norvegicus, andDrosophila melanogaster. On the basis oftheir domain combination and function, PKLNKs have been classified mainly into fourcategories: (1) Ligand binding PKLNKs, (2) PKLNKs with extracellular protein-proteininteraction domain, (3) PKLNKs involved in dimerization, and (4) PKLNKs with cytoplasmicprotein-protein interaction module. While members of the first two classes of PKLNKshave transmembrane domain tethered to the PKLNK domain, members of the other twoclasses of PKLNKs are cytoplasmic in nature. The current classification scheme hopes toprovide a convenient framework to classify the PKLNKs from other eukaryotes whichwould be helpful in deciphering their roles in cellular processes.