Question

G proteins: a. bind GTP. b. dephosphorylate ITAMs. c. are transcription factors. d. down modulate immune responses. e. are adhesion molecules.

1) bind GTP.
2) dephosphorylate ITAMs.
3) are transcription factors.
4) down modulate immune responses.
5) are adhesion molecules.

Answer 1

G proteins primarily function to bind GTP and initiate signal transduction pathways in response to ligand binding on G-protein-coupled receptors, leading to downstream cellular effects.

Step-by-step explanation:

G proteins are involved in various cellular processes and their primary role is to bind GTP to transduce signals from extracellular ligands to generate a cellular response. They interact with G-protein-coupled receptors (GPCRs) which, upon binding a ligand, cause the GDP molecule associated with the G-protein's alpha subunit to be exchanged for GTP.

This activation leads to the dissociation of the beta and gamma subunits from the alpha subunit, triggering cellular responses which can involve ion channels or enzymes such as adenylate cyclase, ultimately affecting processes like cAMP production and protein kinase A (PKA) activity.

G-protein-linked receptors bind a ligand and activate a membrane protein called a G-protein. The activated G-protein then interacts with either an ion channel or an enzyme in the membrane. All G-protein-linked receptors have seven transmembrane domains, but each receptor has its own specific extracellular domain and G-protein-binding site.