TY - JOUR
T1 - Salt effects on the conformational stability of the visual G-protein-coupled receptor rhodopsin
AU - Reyes-Alcaraz, Arfaxad
AU - Martínez-Archundia, Marlet
AU - Ramon, Eva
AU - Garriga, Pere
N1 - Funding Information:
This research was supported by grants from Ministerio de Investigación, Ciencia e Innovación (SAF2008-04943-C02-02) and from Comissionat per a Universitats i Recerca del DIUE de la Generalitat de Catalunya (2009 SGR 1402) to P.G. and predoctoral fellowships from CONACYT (Mexico City, Mexico) to A.R.A. and M.M.A.
PY - 2011/12/7
Y1 - 2011/12/7
N2 - Membrane protein stability is a key parameter with important physiological and practical implications. Inorganic salts affect protein stability, but the mechanisms of their interactions with membrane proteins are not completely understood. We have undertaken the study of a prototypical G-protein-coupled receptor, the α-helical membrane protein rhodopsin from vertebrate retina, and explored the effects of inorganic salts on the thermal decay properties of both its inactive and photoactivated states. Under high salt concentrations, rhodopsin significantly increased its activation enthalpy change for thermal bleaching, whereas acid denaturation affected the formation of a denatured loose-bundle state for both the active and inactive conformations. This behavior seems to correlate with changes in protonated Schiff-base hydrolysis. However, chromophore regeneration with the 11-cis-retinal chromophore and MetarhodopsinII decay kinetics were slower only in the presence of sodium chloride, suggesting that in this case, the underlying phenomenon may be linked to the activation of rhodopsin and the retinal release processes. Furthermore, the melting temperature, determined by means of circular dichroism and differential scanning calorimetry measurements, was increased in the presence of high salt concentrations. The observed effects on rhodopsin could indicate that salts favor electrostatic interactions in the retinal binding pocket and indirectly favor hydrophobic interactions at the membrane protein receptor core. These effects can be exploited in applications where the stability of membrane proteins in solution is highly desirable.
AB - Membrane protein stability is a key parameter with important physiological and practical implications. Inorganic salts affect protein stability, but the mechanisms of their interactions with membrane proteins are not completely understood. We have undertaken the study of a prototypical G-protein-coupled receptor, the α-helical membrane protein rhodopsin from vertebrate retina, and explored the effects of inorganic salts on the thermal decay properties of both its inactive and photoactivated states. Under high salt concentrations, rhodopsin significantly increased its activation enthalpy change for thermal bleaching, whereas acid denaturation affected the formation of a denatured loose-bundle state for both the active and inactive conformations. This behavior seems to correlate with changes in protonated Schiff-base hydrolysis. However, chromophore regeneration with the 11-cis-retinal chromophore and MetarhodopsinII decay kinetics were slower only in the presence of sodium chloride, suggesting that in this case, the underlying phenomenon may be linked to the activation of rhodopsin and the retinal release processes. Furthermore, the melting temperature, determined by means of circular dichroism and differential scanning calorimetry measurements, was increased in the presence of high salt concentrations. The observed effects on rhodopsin could indicate that salts favor electrostatic interactions in the retinal binding pocket and indirectly favor hydrophobic interactions at the membrane protein receptor core. These effects can be exploited in applications where the stability of membrane proteins in solution is highly desirable.
UR - http://www.scopus.com/inward/record.url?scp=82955194481&partnerID=8YFLogxK
U2 - 10.1016/j.bpj.2011.09.049
DO - 10.1016/j.bpj.2011.09.049
M3 - Artículo
C2 - 22261069
SN - 0006-3495
VL - 101
SP - 2798
EP - 2806
JO - Biophysical Journal
JF - Biophysical Journal
IS - 11
ER -