Source:http://linkedlifedata.com/resource/umls/id/C0751984
MSH: A class of monomeric, low molecular weight (20-25 kDa) GTP-binding proteins that regulate a variety of intracellular processes. The GTP bound form of the protein is active and limited by its inherent GTPase activity, which is controlled by an array of GTPase activators, GDP dissociation inhibitors, and guanine nucleotide exchange factors. This enzyme was formerly listed as EC 3.6.1.47,NCI: 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.