Question

State the physical and behavioral consequences associated with a GTP-binding protein when it undergoes GTP hydrolysis?

Answer 1

GTP-binding proteins or G proteins plays an important role as G-Protein Coupled Receptors or GPCRs. The G protein is heterotrimeric, composed of three different subunits: α, β and γ. In the inactive form G proteins have GDP bound to it. When the receptor is activated The bound GDP of G protein is exchanged with GTP from cytosol. The β and γ sub-units of G protein dissociate from the α sub-unit as a βγ dimer, and Gα, with its bound GTP binds to the nearby effector enzyme, altering its activity. The effector enzyme then causes a change in the cytosolic concentration of a low molecular weight metabolite or inorganic ion, which acts as a second messenger to activate or inhibit one or more downstream targets, often protein kinases.

Here, the Detachment of β and γ sub-units from G protein is the physical consequence of GTP hydrolysis and the attachment of G protein with effector enzyme and thus altering its activity is the behavioral consequence of GTP hydrolysis.