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ligand-binding domain of the CaSR calcium-sensing receptor, a member of the family C receptors within the G-protein coupled receptor superfamily Ligand-binding domain of the CaSR calcium-sensing receptor, which is a member of the family C receptors within the G-protein coupled receptor superfamily. CaSR provides feedback control of extracellular calcium homeostasis by responding sensitively to acute fluctuations in extracellular ionized Ca2+ concentration. This ligand-binding domain has homology to the bacterial leucine-isoleucine-valine binding protein (LIVBP) and a leucine binding protein (LBP). CaSR is widely expressed in mammalian tissues and is active in tissues that are not directly involved in extracellular calcium homeostasis. Moreover, CaSR responds to aromatic, aliphatic, and polar amino acids, but not to positively charged or branched chain amino acids, which suggests that changes in plasma amino acid levels are likely to modulate whole body calcium metabolism. Additionally, the family C GPCRs includes at least two receptors with broad-spectrum amino acid-sensing properties: GPRC6A which recognizes basic and various aliphatic amino acids, its gold-fish homolog the 5.24 chemoreceptor, and a specific taste receptor (T1R) which responds to aliphatic, polar, charged, and branched amino acids, but not to aromatic amino acids. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",