PURIFICATION OF A PROTEIN FROM NITELLOPSIS-OBTUSA CELLS AND ITS INVOLVEMENT IN THE REGULATION OF POTENTIAL-DEPENDENT CA2+ CHANNELS

A protein was isolated from the thermostable protein fraction of N. ob tusa cells and purified by hydrophobic chromatography on phenyl-Sephar ose and affinity chromatography on melittin-Sepharose. In 15% polyacry lamide gel, the protein has an electrophoretic mobility corresponding to M(r) 17,000 in the presence of 1 mM Ca2+ and M(r) no higher than 19 ,000 in the presence of 1 mM EGTA. Introduction of the protein isolate d to a perfused N. obtusa cell affects the electric parameters of the plasmalemma Ca2+ channels. This influence shows up as a change in I-Ca 2+, as well as an activation of the electrogenous processes in the pla smalemma. The protein produces restoration of I-Ca2+ in the Ca2+ chann els blocked by chlorpromazine. Possible mechanisms of involvement of t his protein in regulation of the functional state of potential-depende nt Ca2+ channels of N. obtusa plasmalemma are assumed.