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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.

A new adsorption chromatography procedure for the purification of calmodulin from bovine brain was developed using polymeric adsorbent 3520. Calmodulin was first isolated by DEAE-Cellulose column chromatography and further purified to apparent homogeneity following elution with 50% ethanol from the adsorbent column. Polyacrylamide gel electrophoresis showed one band either in the presence of Ca2+ or EGTA. The polymeric adsorbent 3520 is a non-polar polymer lacking exchangeable groups. The selective adsorption of calmodulin is based on hydrophobic interaction within the matrix, and is Ca2+ independent. Neither high salt (0.5 M NaC1) nor EGTA (5 mM) was able to elute the CaM from the adsorption column whereas ethanol (50%) eluted it completely. This method is simple to use and it provides highly purified calmodulin with high yield.