Accession Number : ADA187704

Title :   Acetylcholine Receptors in Model Membranes: Structure/Function Correlates.

Descriptive Note : Annual rept. 1 Sep 84-31 Dec 85; Final rept. 1 Sep 82-31 Dec 85,

Corporate Author : CALIFORNIA UNIV SAN DIEGO LA JOLLA

Personal Author(s) : Montal, Mauricio

PDF Url : ADA187704

Report Date : Dec 1985

Pagination or Media Count : 104

Abstract : The nicotinic cholinergic receptor (AChR*) from Torpedo californica electric organ and the voltage sensitive sodium channel from rat brain were purified and thereafter reconstituted into lipid vesicles as well as into planar lipid bilayers. The reconstituted membrane displayed the biophysical, pharmacological and immunochemical properties characteristic of these channel proteins in vivo. A detailed kinetic analysis of channel gating demonstrated the existence of two channel open states. For acetylcholine (ACh), the typical values of the time constants of the short-lived and long-lived open states were about 0.5 ms and about 4 ms. The frequency of occurrence of the long-lived state increased with ACh concentration. The simplest interpretation is that both singly and doubly liganded states of the AChR undergo transitions to the open conformation. Channel opening was voltage dependent and favored by depolarization. Probability density analysis of dwell times in the open and closed states indicates the occurrence of one open state and several distinct closed states. The process of synaptic transduction as well as that of electric excitability has been reduced to studies on the molecular physiology of purified channel proteins in lipid bilayers. The stage is set to investigate how chemical and genetic modifications in the structure of these channel proteins affect their function. Keywords: Tetrodoxin; Sodium; potassium; Chlorine; Rubidium; Reaction kinetics; Electrophysiology.

Descriptors :   *ACETYLCHOLINE, *PROTEINS, *MEMBRANES(BIOLOGY), BRAIN, CAVITIES, CHLORINE, CHOLINERGIC NERVES, CONSTANTS, DEPOLARIZATION, DWELL TIME, ELECTRIC POWER, ELECTROPHYSIOLOGY, GENETICS, IMMUNOCHEMISTRY, IN VIVO ANALYSIS, LIPIDS, LONG LIFE, MODELS, MODIFICATION, NICOTINIC ACID, ORGANS(ANATOMY), PHYSIOLOGY, POTASSIUM, PROBABILITY DENSITY FUNCTIONS, PURIFICATION, RATS, REACTION KINETICS, RUBIDIUM, SENSE ORGANS, SENSES(PHYSIOLOGY), SENSITIVITY, SODIUM, TIME, VOLTAGE, BIOELECTRICITY, BIOCHEMISTRY, FISHES, ION EXCHANGE, MOLECULE MOLECULE INTERACTIONS

Subject Categories : Anatomy and Physiology

Distribution Statement : APPROVED FOR PUBLIC RELEASE