ABSTRACT
Proteins that bind guanosine triphosphate (GTP) and converted to guanosine diphosphate (GDP) during cell signal tranduction. These heterotrimeric proteins are active when GTP occupies the guanine binding site and inactive when it anchors GDP. The two types of G proteins include the trimeric (
α
,
β
,
γ
) receptor-associated G protein and the small G proteins, including Ras and Raf, which function downstream of numerous transmembrane signaling events. Trimeric GTP-binding proteins are associated with parts of numerous cell surface receptors in the cytoplasm, including chemokine receptors.
