Sarcoplasmic reticulum V. The structure of sarcoplasmic reticulum membranes

Abstract

Electron microscope analysis of skeletal muscle microsomes was carried out by negative staining with potassium phosphotungstate. The size and shape of microsomes are influenced by species differences, the conditions of preparation and storage. The outer surface of the microsomal membrane is covered by subunits of 40 Å diameter, with center to center separation of 90–120 Å. Chemical modification of microsomal membrane by treatment with phospholipase C, digitonin, or trypsin produced characteristic changes in the surface structure, shape or size of microsomes, parallel with the loss of Ca 2+ transport function. The surface structure of microsomes does not indicate temperature-dependent structural changes of the kind observed on liver cell surface membranes, and the Arrhenius plot of ATPase activity is linear.