Fig. 4

Phylogeny of putative rhoptry protein kinase (ROPK) families and conserved catalytic domains in Eimeria tenella, E. falciformis and Cyclospora cayetanensis. a Phylogenetic relationship among ROPKs. The neighbor-joining phylogenetic tree was constructed based on genetic distances calculated using the maximum composite likelihood method. Numbers on branches are percent bootstrap values >50 from 1,000 replications. The ROPKs from C. cayetanensis are shown in bold. b Catalytic kinase subdomains and key residues of ROPK subfamilies. The catalytic lysine in subdomain II and aspartic acids in subdomain VIb and VII are considered the key residues in active protein kinases. Their presence along with five other residues in different subdomains suggests that sub-families ROP21/27, ROP35, and ROPK-Eten1 are active protein kinases; the remaining sub-families are either inactive or potentially non-canonical rhoptry kinases. In C. cayetanensis, at least four ROPKs, including cyc_02428 from the ROP21/27 subfamily, cyc_03158 from the ROP35 subfamily, cyc_00989 and cyc_00988 from the ROPK-Eten1 subfamily, are active protein kinases