Figure 1.

Domain diversity of representative protein kinases belonging to various subfamilies of protein kinases extracted from the KinG database. Protein kinase domains are shown in red. (a) Domain combination of protein kinases with the RGS domains characteristic of the AGC_4 subfamily of protein kinases, involved in desensitization of G-protein-coupled receptors. PH, pleckstrin homology domain. Protein kinase representatives from this family are found in H.sapiens, D.melanogaster and C.elegans. Homologues of this subfamily of kinases are not found in S.cerevisiae. (b) Protein kinases with domains known to be involved in ubiquitination. UBA, ubiquitin-associated domain; Usp, universal stress protein domain; U-box, modified ring finger domain found in proteins involved in ubiquitination. UBA-domain-containing protein kinases are found in the CAMK, AGC and PTK subfamilies of A.thaliana, H.sapiens and D.melanogaster. Protein kinases containing ubiquitin domains encoded in H.sapiens and D.melanogaster belong to the CAMK subfamily. Arabidopsis thaliana in addition encodes another class of ubiquitin-related protein kinases with a U-box, which belong to the plant receptor kinase subfamily.