The phosphorylation of lipid transfer protein CaMBP10

Calmodulin-binding protein-10 (CaMBP10) was isolated previously from Chinese cabbage and identified as a member of the lipid transfer protein family. In this study, we found that CaMBP10 was phosphorylated in a calcium(Ca(2+))-dependent manner, and the phosphorylation was inhibited by calmodulin (CaM) antagonists. In-gel kinase assay revealed that the phosphorylation of CaMBP10 was catalyzed by a 45 kDa protein kinase, which underwent autophosphorylation in the presence of Ca(2+). Immunoblotting assay further identified this kinase as a calcium-dependent protein kinase (CDPK). In addition, the phosphorylation site was mapped to the C-terminal region of CaMBP10, where the CaM-binding domain resides. These results provide novel insights into the molecular mechanisms that regulate CaMBP10 functions.