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The Molecular Switching Mechanism at the Conserved D(E)RY Motif in Class-A GPCRs.

Sandoval A, Eichler S, Madathil S, Reeves PJ, Fahmy K, Böckmann R (2016)

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Publication Language: English

Publication Status: Published

Publication Type: Journal article, Original article

Publication year: 2016

Journal

Book Volume: 111

Pages Range: 79-89

Journal Issue: 1

DOI: 10.1016/j.bpj.2016.06.004

Abstract

The disruption of ionic and H-bond interactions between the cytosolic ends of transmembrane helices TM3 and TM6 of class-A (rhodopsin-like) G protein-coupled receptors (GPCRs) is a hallmark for their activation by chemical or physical stimuli. In the bovine photoreceptor rhodopsin, this is accompanied by proton uptake at Glu(134) in the class-conserved D(E)RY motif. Studies on TM3 model peptides proposed a crucial role of the lipid bilayer in linking protonation to stabilization of an active state-like conformation. However, the molecular details of this linkage could not be resolved and have been addressed in this study by molecular dynamics (MD) simulations on TM3 model peptides in a bilayer of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC). We show that protonation of the conserved glutamic acid alters the peptide insertion depth in the membrane, its side-chain rotamer preferences, and stabilizes the C-terminal helical structure. These factors contribute to the rise of the side-chain pKa (> 6) and to reduced polarity around the TM3 C terminus as confirmed by fluorescence spectroscopy. Helix stabilization requires the protonated carboxyl group; unexpectedly, this stabilization could not be evoked with an amide in MD simulations. Additionally, time-resolved Fourier transform infrared (FTIR) spectroscopy of TM3 model peptides revealed a different kinetics for lipid ester carbonyl hydration, suggesting that the carboxyl is linked to more extended H-bond clusters than an amide. Remarkably, this was seen as well in DOPC-reconstituted Glu(134)- and Gln(134)-containing bovine opsin mutants and demonstrates that the D(E)RY motif is a hydrated microdomain. The function of the D(E)RY motif as a proton switch is suggested to be based on the reorganization of the H-bond network at the membrane interface.

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How to cite

APA:

Sandoval, A., Eichler, S., Madathil, S., Reeves, P.J., Fahmy, K., & Böckmann, R. (2016). The Molecular Switching Mechanism at the Conserved D(E)RY Motif in Class-A GPCRs. Biophysical Journal, 111(1), 79-89. https://doi.org/10.1016/j.bpj.2016.06.004

MLA:

Sandoval, Angelica, et al. "The Molecular Switching Mechanism at the Conserved D(E)RY Motif in Class-A GPCRs." Biophysical Journal 111.1 (2016): 79-89.

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