Ca2+-dependent interaction of calcyclin with membrane.

The presence of calcyclin in the microsomal fraction of Ehrlich ascites tumor cells was detected using polyclonal antibodies. Association of calcyclin with the microsomes depended on the presence of calcium ions in the buffer used for cell fractionation. The interaction of calcylcin with Ehrlich ascites tumor cells microsomes was confirmed in the in vitro conditions by cosedimentation assay using exogenous calcyclin. It was shown that phospholipids extracted from natural membranes and purified phosphatydylserine or phosphatydylcholine were not involved in the binding. Instead, several low molecular weight polypeptides in the Triton X-100 resistant membrane fraction were found to interact with calcyclin.