Which of the following events normally activates a GTP-binding protein? a). GTP hydrolysis by the protein Activation of an upstream GTPase-activating proteinb). Activation of an upstream guanine nucleotide exchange factorc). Phosphorylation of a bound GDP molecule by an upstream phosphorylased). Pi release after GTP hydrolysis

Answer;

b). Activation of an upstream guanine nucleotide exchange factor

Explanation; When a ligand activates the G protein-coupled receptor, it induces a conformational change in the receptor that allows the receptor to function as a guanine nucleotide exchange factor (GEF) that exchanges GDP for GTPthus turning the G protein-coupled receptor on. The activated G-protein then dissociates into an alpha (G-alpha) and a beta-gamma complex.