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Free backbone carbonyls mediate rhodopsin activation.

Naoki Kimata¹, Andreyah Pope¹, Omar B Sanchez-Reyes¹

¹Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York, USA.

Nature Structural & Molecular Biology

|July 5, 2016

Summary

Conserved prolines in G-protein-coupled receptors (GPCRs) act as hinges. Their C=O groups stabilize inactive rhodopsin structure via hydrogen bonds, which are released upon light activation, enabling receptor repacking.

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Area of Science:

Biochemistry
Structural Biology
Membrane Protein Dynamics

Background:

Conserved prolines in transmembrane helices of G-protein-coupled receptors (GPCRs) are hypothesized to function as hinges.
These prolines can influence receptor structure and conformational flexibility through hydrogen-bonding interactions of their associated C=O groups.

Purpose of the Study:

To investigate the structural and functional roles of conserved prolines in family A GPCRs.
To elucidate the specific contributions of proline C=O groups to receptor stabilization and conformational changes.

Main Methods:

Solid-state Nuclear Magnetic Resonance (NMR) spectroscopy.
Focus on bovine rhodopsin, a well-characterized visual receptor subfamily GPCR.

Main Results:

Identified free backbone C=O groups on helices H5 and H7 of rhodopsin stabilize the inactive state via hydrogen bonds to adjacent residues.
Demonstrated light-induced retinal isomerization releases these hydrogen-bonding interactions.
Observed facilitated repacking of helices H5 and H7 onto the transmembrane core upon activation.

Conclusions:

Proline C=O groups play crucial roles in stabilizing the inactive GPCR conformation.
These interactions are dynamically regulated during receptor activation, facilitating structural rearrangements.
Provides insights into the multifaceted roles of prolines in membrane protein structure and function.