Amino acid residues in third intracellular loop of melanocortin 1 receptor are involved in G-protein coupling.

摘要: To delineate domains essential for G-protein coupling in melanocortin 1 receptor (MC1R), we mutated polar and basic residues to alanine at eleven positions the putative third intracellular loop determined consequent changes ligand binding generation of second messenger cAMP. Results demonstrate that affinity was not affected by any mutations. However, every mutant displayed reduced functional response as compared wild type receptor. Replacement (K226, R227, Q228, R229, H232, Q233 K238) present half resulted an almost complete loss response. The results have demonstrated amino acid C-terminal portion MC1R are involved a region four acids, K226-R227-Q228-R229 is G-protein.