MOLECULAR STUDIES OF CA++ TRANSPORT IN NERVE AND RETINA

神经系统的电活动是由一类蛋白质产生的

The electrical activity of the nervous system is produced by a class of protein molecules, imbedded in the nerve cell membrane, that catalyze the active pumping and passive gating of specific ions. Our laboratory has been involved in the identification, isolation, and in vitro characterization of certainkey neuronal ion transport proteins from mammalian brain: an ATP-dependent Ca ions transport system involved in the regulation of neurotransmitter release from nerve terminals, and a voltage-sensitive Na ion gate that is responsible for the neuronal "action potential." In recent years, our laboratory has developed a new approach, "transport specific fractionation," for purification of membrane transport systems. Using this technique, we have obtained purification of the neuronal Ca ions transport protein to near homogeneity (approximately 100-fold). We are now in the process of studying its possible regulation by the opiates and other endogenous mechanisms and are purifying other intraterminal Ca ions transport systems. In parallel, we have for the first time successfully reconstituted the detergent solubilized, voltage-sensitive Na ion gate and have partially purified it by "transport specific fractionation". We are proceeding to further purify it, if possible to homogeneity. We intend to incorporate vesicles containing the purified Na gate into plannar bilayers, where its electrical properties can be more quantitatively observed. We are producing monoclonal antibodies to the Na gate for immunocytochemistry. We have been studying the regulation of the Na ion gate by endogenous environmental factors.