GTP-binding protein

Function

GTP-binding proteins or G proteins are transmitting signals outside the cell which cause changes within the cell. They act as molecular switches which are on when binding GTP and off when binding GDP. GTP-binding proteins belong to two families: heterotrimeric G proteins^[1] and small GTPases^[2]. The structure of small GTPase is homologous to that of the α subunit of heterotrimeric G protein. See details on GTP-binding protein LepA in LepA.

(human β-2 adrenergic receptor in blue ) in a complex with a heterotrimeric G protein (3 subunits:reddish to orange-brown) and hormone (gold) (3sn6), resolution 3.2Å. The boundaries of the membrane in which the GPCR sits are represented in light green.

Disease

Mutations in heterotrimeric α subunit were identified in endocrine tumors and in McCune-Albright syndrome^[3].

Structural highlights

E. coli small GTPase ERA binds GDP in a cavity formed by 3 highly conserved regions^[4].