Transmembrane residues of the parathyroid hormone (PTH)/PTH-related peptide receptor that specifically affect binding and signaling by agonist ligands.
Polar residues within the transmembrane domains (TMs) of G protein-coupled receptors have been implicated to be important determinants of receptor function. We have identified mutations at two polar sites in the TM regions of the rat parathyroid hormone (PTH)/PTH-related peptide receptor, Arg-233 in TM 2 and Gln-451 in TM 7, that caused 17-200-fold reductions in the binding affinity of the agonist peptide PTH-(1-34) without affecting the binding affinity of the antagonist/partial agonist PTH-(3-34). When mutations at the TM 2 and TM 7 sites were combined, binding affinity for PTH-(1-34) was restored to nearly that of the wild type receptor. The double mutant receptors, however, were completely defective in signaling cAMP or inositol phosphate production in response to PTH-(1-34) agonist ligand. The results demonstrate that Arg-233 and Gln-451 have important roles in determining agonist binding affinity and transmembrane signaling. Furthermore, the finding that residues in TM 2 and TM 7 are functionally linked suggests that the TM domain topology of the PTH/PTH-related peptide receptor may resemble that of receptors in the rhodopsin/beta-adrenergic receptor family, for which structural and mutagenesis data suggest interactions between TMs 2 and 7.
Gardella
T J
TJ
Endocrine Unit, Department of Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, USA.
Luck
M D
MD
Fan
M H
MH
Lee
C
C
D000595:Amino Acid Sequence; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D004789:Enzyme Activation; D006801:Humans; D008969:Molecular Sequence Data; D011485:Protein Binding; D051381:Rats; D044168:Receptor, Parathyroid Hormone, Type 1; D018016:Receptors, Parathyroid Hormone / Q000737:chemistry / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D010738:Type C Phospholipases / Q000378:metabolism
D044168:Receptor, Parathyroid Hormone, Type 1; D018016:Receptors, Parathyroid Hormone; D010738:Type C Phospholipases