G-protein

In <a href="Cell signalling pathways">signalling pathways</a>, G-proteins act as transducers and convert signals from one form to another form, by binding to other proteins in the plasma membrane of a cell. They can bind <a href="GTP">GTP</a> or <a href="GDP">GDP</a>. G-proteins can be either trimeric or monomeric. Monomeric G-proteins transduce signals from <a href="Enzyme-coupled Receptor">enzyme-linked receptors</a> whereas trimeric G-proteins transduce signals from <a href="G-protein Coupled Receptor">G-protein linked receptors</a> B Alberts et al. (2008) Molecular Biology of the Cell, 5th Edition, New York:Garland Science. <a href="Ion channels">Ion channels</a> can be activated by binding of G-proteins. This can slow the heart beat when G-proteins bind to <a href="Muscarinic receptors">muscarinic receptors</a>, as they increase the permeability of a neurone to K⁺ ions, which decreases the rate of neurone firing Purves D, Augustine GJ, Fitzpatrick D, et al (2001) Neuroscience (2nd ed.) Sunderland MA: Sinauer Associates.