Effects of calmodulin and calmodulin binding protein BP-10 on phosphorylation of thylakoid membrane protein

Light-induced phosphorylation of endogenous thylakoid membrane protein can be inhibited markedly by a novel inhibitor CaMBP-10 which is discovered and isolated from plant. The inhibitory effect of BP-10 can be eliminated by addition of CaM. At the same time, the phosphorylation can also be inhibited by EGTA or CaM antagonists, such as TFP (trifluoperazine) and W-7 (N-(6-aminohexyl)-5-chloro-l-naphthalene sulfonamide). This result implies that (i) Ca(2+) and CaM most likely participate in and regulate plant photosynthesis; (ii) the kinase that catalyzes thylakoid membrane protein phosphorylation can be regulated by Ca(2+) and CaM. However, the further experiments indicate that BP-10 has no effect on dephosphorylation of thylakoid phosphoproteins.