Thursday, October 13, 2011

Ligand-gated Ion Channels

Ligand-gated ion channels are neurotransmitter receptors on the cell membrane which open or close in response to binding of a neurotransmitter, which is a chemical messenger. Ligand-gated ion channels consist of different subunits that are inserted into the cell membrane. Binding of the neurotransmitter to the specific receptor causes the channel to become permeable to certain ions, such as potassium (K+) and sodium (Na+). The prototypic ligand-gated ion channel is the nicotinic acetylcholine receptor, which is composed of a pentamer of protein subunits, with two binding sites for acetylcholine, which, when bound, alter the receptor's configuration and cause an internal pore to open.