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 1 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 .