<unk> s, short for guanine nucleotide binding<unk> s, are a family of<unk> s involved in second messenger cascades. Their nomenclature originates from their ability to function as "molecular switches", alternating between an inactive guanosine diphosphate (GDP) and activated guanosine triphosphate (GTP) bound state, ultimately going on to regulate downstream cell processes.<unk> s belong to the larger group of enzymes called GTPases.
G protein
Rho GTPase
Rho
JP-8
STAT protein
Receptor 
Janus kinase
Calmodulin