試題詳解

29. Which of the following descriptions about G protein-coupled receptors (GPCR) is (are) CORRECT?
(A) GPCRs constitute one of the largest protein families encoded by the mammalian genomes, including adrenalin receptors, odorant receptors, rhodopsin and EGF (epidermal growth factor) receptors.
(B) The general structure of GPCRs includes seven transmembrane a-helices with the N-terminus facing the extracellular space and C-terminus in the cytosol.
(C) Activation of the GPCR by its ligand triggers dissociation of GDP from the B-subunit of the G protein, which in turns activates the a-subunit.
(D) The specificity of GPCR signaling is determined solely by the unique ligand that a receptor binds.
(E) Desensitization of GPCR signaling requires receptor-mediated endocytosis that depends on clathrin, AP2 and ẞ-arrestin.