Studies on plant extracellular calmodulin by lanthanide luminescence probe

Plant extracellular calmodulin (CaM) has been purified from cauliflower and identified with NAD kinase(NADK) activation and inhibition effect of CaM a ntagonist W7, Tb-3.1 fluorescence titration showed that extracellular CaM c ontained four metal-binding sites, The excitation spectrum and emission spe cturm indicated that extracellular CaM contained one tyrosine residue which could transfer energy to bound Tb3+. Based on Forster type nonradiative en ergy transfer theory, the distances of Tyr-->sites III, IV have been determ ined, these are 1. 104 nm(Tyr --> III, site) and 1. 056 nm(Tyr --> N, site) . By studing the effect of CaM antagonist W7 and CaM antibody on Tb3+-sensi tized fluorescence, it was found that the binding sites of W7 and antibody were located on the c-terminal part of plant extracellular CaM which contai ns domain III and domain IV.