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Hydration Mediated G‐Protein‐Coupled Receptor Activation
Author(s) -
Weerasinghe Nipuna,
Fried Steven D.E.,
Perera Suchithrang M.D.C.,
Chawla Udeep,
Brown Michael F.
Publication year - 2018
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2018.32.1_supplement.lb64
Subject(s) - osmolyte , chemistry , biophysics , rhodopsin , g protein coupled receptor , g protein , receptor , biochemistry , biology , retinal
G‐protein–coupled receptors (GPCRs) are the largest family of cell membrane‐bound receptors in humans. They are involved with sensing molecules outside the cell and the subsequent transduction of this signal to activate intracellular signaling pathways. Rhodopsin is a canonical GPCR, which upon photoactivation undergoes a series of conformational changes leading to a chemical equilibrium between closed inactive Metarhodopsin I (Meta‐I ) and open active Metarhodopsin II (Meta‐II ) states. According to molecular dynamics simulation work carried out by Nicholas Leioatts et al [1] activation of rhodopsin leads to an increase in hydrated protein volume in the active Meta‐II state. Using UV‐visible spectroscopy, we tested this hypothesis by evaluating how the Meta‐I/Meta‐II equilibrium is influenced by changing the osmotic pressure of aqueous environment of the protein in native lipid membrane. We discovered that osmolytes of varying molar mass affect rhodopsin activation differently by altering the Meta‐I/Meta‐II equilibrium. Large osmolytes shift the equilibrium to the inactive Meta‐I state, in conjunction with the efflux of water. By contrast, small osmolytes shift the equilibrium toward Meta‐II state. We attribute the shift caused by large osmolytes to the ability of these osmolytes to remove large quantities of water from the protein interior. Since these osmolytes are large, they are entropically hindered from penetrating into the protein core, and thus withdraw water to collapse the protein into the inactive Meta‐I state. Small osmolytes are able to enter into the protein core, minimizing the effect of withdrawing water from the protein as seen with larger osmolytes, although the reversal effect is still not fully understood. Further work will seek to determine whether this effect is robust with respect to type of osmolyte (e.g. Polyvinyl Pyrrolidone, dextran), and how the effect is altered when the lipid environment of the protein is changed. This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .