CaM BP-10 (BP-10) is anovel endogenous calmodalin (CaM )-binding Protein tha was observed in andisolated from Plant. In our prelidrimpstudies it has been shown tha BP-10specifically inhibits adrin (IAA)-in-duced coleoptile elongallon and pbonsecrehon. In oIder to inveshgatewhether BP10 inhibitS Picton secrehonand cell elongaion thidgh inhibitingthc achvity of Plasrna mernbare (PM)H+ -ATPase, the effect of BP-10 on theachvity of wheat coleoptile PM H+ -AT-Pase has been studied. It was observedtha neither IAA nor BP-10 had any effect on the achvity of PM H+ -ATPaSein vitro. In vho, however, the activity0f Al-treated PM H+-ATPaSe washigher than tha of the control, and BP-10 peilicanx iwhbital atinduedachvity by 87- 8% (rig. 1) - In addi-hon, the inhibitory effect cotild be re-versed by IAA after BPIO was removedfrom the mediurn, and it could also beovercome bV the addihon of CaM.Therefore, it appears that BP-10 in-hibits cell responses to andn by affect-ing the achvity of PM H+ -ATPase andthereby inhibiting Proton secrehon. As aresult, cell elongaon is inhibited. AndCaM is also involved in this pmeess-
