Receptors and Transduction Mechanisms I: Receptors Coupled Directly to Ion Channels

Abstract

The common feature that allows neurons and other cells to respond to extracellular signals is the presence of specific receptors in the plasma membrane, which may be similar in their structure and functional properties in different kinds of cells. There may be several different kinds of receptors for individual neurotransmitters. Many receptors can be grouped into families based on structural, functional, and regulatory homologies that are far more extensive than had been appreciated previously. One such family is that of the ligand-gated ion channels, whose members were first linked on the basis of a functional criterion—direct coupling between the receptor and the ion channel whose activity it regulates. Evolution has allowed the ligand specificity of the receptor site and the ion selectivity of the channel pore to diverge. However, the essential overall structural design of the ligand-gated receptor–channel complex has been preserved.