Imidazole and sequestration of calcium ions by sarcoplasmic reticulum.

Abstract

SARCOTUBULAR, fragments prepared from homogenates of skeletal muscle are able to sequester vigorously calcium ions if ATP is available, and they show the activity of Mg-ATPase and Ca-ATPase which are thought to serve in the energy requiring sequestration of calcium ions. Although these functions have been the subject of much experimentation, little is known about their molecular bases. The uptake and release of calcium ions by the sarcotubular system are believed to be an integral part of excitation–contraction coupling and relaxation of muscle, and so it is important to understand the molecular mechanisms which underlie these processes. Hasselbach and Seraydarian1 have reported that certain sulphydryl groups of the sarcotubular membranes play an important part in both the uptake of calcium ions and the related ATPase activities. Experiments carried out in our laboratory, however, indicate that a functional group other than the sulphydryl is also involved in these activities.