Small G Protein

**Semantic type:** Amino Acid, Peptide, or Protein|Enzyme

**Definition:** A class of small GTP-binding regulatory proteins regulated by G protein coupled receptors that act as switches in signal transduction pathways. The nature of the nucleotide bound to the protein determines its activity: GTP in the active state, GDP in the inactive state. The prototype for this class of proteins is the cellular proto-oncogene RAS.