Fig. 1: XopC2 represents a family of effector kinases.

a Sequence alignment of catalytic motifs in different families of protein kinases. Eight representative protein kinases with the highest scores in the output list from HHpred searches against the conserved motif (391–417 amino-acid residues) of XopC2 were aligned with ClustalX, and the conserved catalytic sites were highlighted in purple boxes. b Schematic diagrams of secondary structures of canonical kinases and XopC2. The top row showed the generally conserved secondary structure profile of canonical kinases³⁸. Twelve subdomains and conserved structural characteristics were marked based on standard kinase annotations⁷⁰. The bottom row showed the secondary structure profile of XopC2. The key conserved residues of canonical kinases and XopC2 were numbered based on the human canonical protein kinase A (PKA) and XopC2^Xoc, respectively, and were shown in the middle. c In vitro purified XopC2 was autophosphorylated, while the point mutations D391A and N396A reduced the autophosphorylation of XopC2 as revealed by in vitro kinase assays. Upper panel, His6-XopC2 phosphorylation was detected by autoradiography. Lower panel, the proteins were stained with Coomassie brilliant blue (CBB) as a loading control. The experiments were independently repeated 3 times with similar results.