Interactions between conserved residues in transmembrane helices 1, 2, and 7 of the thyrotropin-releasing hormone receptor.
The roles of conserved residues in transmembrane helices (TMs) of G protein-coupled receptors have not been well established. A computer-generated model of the thyrotropin-releasing hormone receptor (TRH-R) indicated that conserved Asp-71 (TM-2) could interact with conserved asparagines 316 (TM-7) and 43 (TM-1). To test this model, we constructed mutant TRH-Rs containing polar or alanine substitutions of these residues. The maximal activities of N43A and N316A TRH-Rs were diminished, whereas D71A (Perlman, J. H., Nussenzveig, D. R., Osman, R., and Gershengorn, M. C. (1992) J. Biol. Chem. 267, 24413-24417) and N43A/N316A TRH-Rs were inactive. Computer models of D71A and N43A/N316A TRH-Rs show similar changes from native TRH-R in their TM bundle conformations. The inactivity and the similarity of the computer models of D71A and N43A/N316A TRH-Rs are consistent with the idea that Asp-71 bridges Asn-43 and Asn-316 and suggest that activity is critically dependent on these interactions. The conservation of these residues suggests these specific interactions involving TMs 1, 2, and 7 may be structurally important for all members of the rhodopsin/beta-adrenergic receptor subfamily of G protein-coupled receptors.
Perlman
J H
JH
Division of Molecular Medicine, Department of Medicine, Cornell University Medical College and The New York Hospital, New York, New York 10021, USA.
Colson
A O
AO
Wang
W
W
Bence
K
K
Osman
R
R
Gershengorn
M C
MC
D000595:Amino Acid Sequence; D000818:Animals; D001216:Asparagine; D001224:Aspartic Acid; D001665:Binding Sites; D019556:COS Cells; D003198:Computer Simulation; D017124:Conserved Sequence; D007295:Inositol Phosphates / Q000378:metabolism; D008961:Models, Structural; D016297:Mutagenesis, Site-Directed; D017354:Point Mutation; D017433:Protein Structure, Secondary; D018025:Receptors, Thyrotropin-Releasing Hormone / Q000737:chemistry* / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D013816:Thermodynamics; D013973:Thyrotropin-Releasing Hormone / Q000737:chemistry* / Q000378:metabolism* / Q000494:pharmacology; D014162:Transfection
D007295:Inositol Phosphates; D018025:Receptors, Thyrotropin-Releasing Hormone; D011994:Recombinant Proteins; D001224:Aspartic Acid; D013973:Thyrotropin-Releasing Hormone; D001216:Asparagine