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PMID: 19706606 Published · ppublish English Journal Article Research Support, Non-U.S. Gov't

Lipid protein interactions couple protonation to conformation in a conserved cytosolic domain of G protein-coupled receptors.

The Journal of biological chemistry ·Vol. 284 ·No. 42 ·2009-10-16 ·Pages 28801-9

Madathil S, Fahmy K

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.

MeSH Terms
Amino Acid Motifs Animals Cattle Cytosol/metabolism Hydrogen-Ion Concentration Ligands Lipids/chemistry Micelles Photoreceptor Cells, Vertebrate/metabolism Protein Structure, Secondary Protein Structure, Tertiary Proteins/chemistry Protons Receptors, G-Protein-Coupled/chemistry Rhodopsin/chemistry Spectrometry, Fluorescence/methods
Chemicals
Ligands Lipids Micelles Proteins Protons Receptors, G-Protein-Coupled Rhodopsin
Authors & Affiliations
2 authors, click to expand affiliations / ORCID
Madathil Sineej
Division of Biophysics, Institute of Radiochemistry, Forschungszentrum Dresden-Rossendorf, PF 510119, D-01314 Dresden, Germany.
Fahmy Karim
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Article Info
Journal
The Journal of biological chemistry
Abbr.
J Biol Chem
ISSN
1083-351X
DOI
10.1074/jbc.M109.002030
Published
2009-10-16
Epub
2009-00-25
Pages
28801-9
Language
English
Region
United States
NLM ID
2985121R
PMCID
PMC2781426
Subset
IM
External Links
PubMed source DOI: 10.1074/jbc.M109.002030 PMC Full Text View journal details
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