title: Lipid protein interactions couple protonation to conformation in a conserved cytosolic domain of G protein-coupled receptors.
abstract: The visual photoreceptor rhodopsin is a prototypical class I (rhodopsin-like) G protein-coupled receptor. Photoisomerization of the covalently bound ligand 11-cis-retinal leads to restructuring of the cytosolic face of rhodopsin. The ensuing protonation of Glu-134 in the class-conserved D(E)RY motif at the C-terminal end of transmembrane helix-3 promotes the formation of the G protein-activating state. Using transmembrane segments derived from helix-3 of bovine rhodopsin, we show that lipid protein interactions play a key role in this cytosolic "proton switch." Infrared and fluorescence spectroscopic pK(a) determinations reveal that the D(E)RY motif is an autonomous functional module coupling side chain neutralization to conformation and helix positioning as evidenced by side chain to lipid headgroup Foerster resonance energy transfer. The free enthalpies of helix stabilization and hydrophobic burial of the neutral carboxyl shift the side chain pK(a) into the range typical of Glu-134 in photoactivated rhodopsin. The lipid-mediated coupling mechanism is independent of interhelical contacts allowing its conservation without interference with the diversity of ligand-specific interactions in class I G protein-coupled receptors.
authors.affiliation: Division of Biophysics, Institute of Radiochemistry, Forschungszentrum Dresden-Rossendorf, PF 510119, D-01314 Dresden, Germany.
authors.forename: Sineej
authors.initials: S
authors.lastname: Madathil
authors.forename: Karim
authors.initials: K
authors.lastname: Fahmy
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D002417:Cattle; D003600:Cytosol / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008024:Ligands; D008055:Lipids / Q000737:chemistry*; D008823:Micelles; D020419:Photoreceptor Cells, Vertebrate / Q000378:metabolism; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000737:chemistry; D011522:Protons; D043562:Receptors, G-Protein-Coupled / Q000737:chemistry*; D012243:Rhodopsin / Q000737:chemistry; D013050:Spectrometry, Fluorescence / Q000379:methods
chemical_list: D008024:Ligands; D008055:Lipids; D008823:Micelles; D011506:Proteins; D011522:Protons; D043562:Receptors, G-Protein-Coupled; D012243:Rhodopsin
references.citation: Photochem Photobiol. 2009 Mar-Apr;85(2):437-41
references.pmid: 19267869
references.citation: Mol Pharmacol. 2002 May;61(5):1025-32
references.pmid: 11961120
references.citation: Nature. 2008 Jul 10;454(7201):183-7
references.pmid: 18563085
references.citation: Proc Natl Acad Sci U S A. 2002 Apr 30;99(9):5982-7
references.pmid: 11972040
references.citation: J Mol Biol. 2007 Dec 14;374(5):1251-69
references.pmid: 17997412
references.citation: Proc Natl Acad Sci U S A. 2006 Oct 31;103(44):16123-8
references.pmid: 17060607
references.citation: Biochemistry. 1993 Jul 20;32(28):7229-36
references.pmid: 8343512
references.citation: Photochem Photobiol. 2007 Mar-Apr;83(2):286-92
references.pmid: 17576345
references.citation: Mol Pharmacol. 2008 May;73(5):1333-8
references.pmid: 18239031
references.citation: Biochemistry. 1994 Sep 13;33(36):10878-82
references.pmid: 7916209
references.citation: J Biol Chem. 2001 Aug 3;276(31):29171-7
references.pmid: 11375997
references.citation: Proc Natl Acad Sci U S A. 2009 Mar 24;106(12):4689-94
references.pmid: 19258456
references.citation: Biopolymers. 2006 Jul;82(4):329-33
references.pmid: 16453309
references.citation: Biophys J. 2006 Dec 15;91(12):4464-77
references.pmid: 17012328
references.citation: J Biol Chem. 1994 Sep 30;269(39):23879-81
references.pmid: 7929034
references.citation: Biochemistry. 2004 Jun 8;43(22):6858-64
references.pmid: 15170322
references.citation: Nature. 1996 Sep 26;383(6598):347-50
references.pmid: 8848049
references.citation: Biochemistry. 1993 Mar 9;32(9):2438-54
references.pmid: 8443184
references.citation: Proc Natl Acad Sci U S A. 1997 Feb 4;94(3):808-13
references.pmid: 9023338
references.citation: Annu Rev Biophys Biomol Struct. 1996;25:287-314
references.pmid: 8800472
references.citation: J Mol Biol. 2004 Mar 26;337(3):713-29
references.pmid: 15019789
references.citation: Science. 2000 Aug 4;289(5480):739-45
references.pmid: 10926528
references.citation: Proc Natl Acad Sci U S A. 2007 Dec 18;104(51):20290-5
references.pmid: 18077356
references.citation: Biophys J. 2000 Dec;79(6):3063-71
references.pmid: 11106612
references.citation: Methods Enzymol. 2000;315:178-96
references.pmid: 10736702
references.citation: Biochemistry. 1974 Jul 30;13(16):3350-9
references.pmid: 4366945
references.citation: Science. 2007 Nov 23;318(5854):1258-65
references.pmid: 17962520
references.citation: Biophys J. 2004 Apr;86(4):2078-100
references.pmid: 15041649
references.citation: Proc Natl Acad Sci U S A. 2008 May 27;105(21):7439-44
references.pmid: 18490656
references.citation: Proc Natl Acad Sci U S A. 1991 Apr 1;88(7):2854-8
references.pmid: 2011594
references.citation: J Am Chem Soc. 2008 Sep 17;130(37):12465-71
references.pmid: 18712874
references.citation: Science. 2007 Nov 23;318(5854):1266-73
references.pmid: 17962519
references.citation: J Mol Biol. 2004 Nov 5;343(5):1409-38
references.pmid: 15491621
references.citation: Biochemistry. 2002 Jul 2;41(26):8298-309
references.pmid: 12081478
references.citation: Biochemistry. 1996 Apr 23;35(16):5109-24
references.pmid: 8611495
references.citation: J Mol Biol. 2007 Mar 2;366(4):1129-41
references.pmid: 17196983
references.citation: Nature. 2008 Jul 24;454(7203):486-91
references.pmid: 18594507
references.citation: Curr Opin Struct Biol. 2008 Dec;18(6):734-40
references.pmid: 18957321
references.citation: Proc Natl Acad Sci U S A. 2008 Nov 18;105(46):17795-800
references.pmid: 18997017
references.citation: Mol Pharmacol. 2009 Jan;75(1):1-12
references.pmid: 18945819
references.citation: J Mol Biol. 2008 Jul 18;380(4):648-55
references.pmid: 18554610
references.citation: J Biol Chem. 2006 Nov 3;281(44):33233-41
references.pmid: 16959786
references.citation: Biochemistry. 2000 Aug 29;39(34):10607-12
references.pmid: 10956053
references.citation: Nature. 2008 Sep 25;455(7212):497-502
references.pmid: 18818650
references.citation: Biochemistry. 2006 May 2;45(17):5538-50
references.pmid: 16634635