G protein

A family of proteins that act as molecular switches in signal transduction pathways by binding and hydrolyzing GTP. They relay signals from G protein-coupled receptors to various intracellular targets, controlling numerous physiological processes.

Named for their ability to bind guanine nucleotides (GTP and GDP), with 'G' standing for guanine. Discovered in the 1970s by Martin Rodbell and Alfred Gilman, who won the Nobel Prize for this work that revolutionized understanding of cellular communication.