Protein-induced bonding perturbation of the rhodopsin chromophore detected by double-quantum solid-state NMR.
We have obtained carbon-carbon bond length data for the functional retinylidene chromophore of rhodopsin, with a spatial resolution of 3 pm. The very high resolution was obtained by performing double-quantum solid-state NMR on a set of noncrystalline isotopically labelled bovine rhodopsin samples. We detected localized perturbations of the carbon-carbon bond lengths of the retinylidene chromophore. The observations are consistent with a model in which the positive charge of the protonated Schiff base penetrates into the polyene chain and partially concentrates around the C13 position. This coincides with the proximity of a water molecule located between the glutamate-181 and serine-186 residues of the second extracellular loop, which is folded back into the transmembrane region. These measurements support the hypothesis that the polar residues of the second extracellular loop and the associated water molecule assist the rapid selective photoisomerization of the retinylidene chromophore by stabilizing a partial positive charge in the center of the polyene chain.
Carravetta
Marina
M
Physical Chemistry Division, Stockholm University, S-106 91 Stockholm, Sweden.
Zhao
Xin
X
Johannessen
Ole G
OG
Lai
Wai Cheu
WC
Verhoeven
Michiel A
MA
Bovee-Geurts
Petra H M
PH
Verdegem
Peter J E
PJ
Kiihne
Suzanne
S
Luthman
Henrik
H
de Groot
Huub J M
HJ
deGrip
Willem J
WJ
Lugtenburg
Johan
J
Levitt
Malcolm H
MH
D002247:Carbon Isotopes; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D011487:Protein Conformation; D012176:Retinoids / Q000737:chemistry*; D012243:Rhodopsin / Q000737:chemistry*; D012545:Schiff Bases / Q000737:chemistry
D002247:Carbon Isotopes; D012176:Retinoids; D012545:Schiff Bases; C121835:retinylidene chromophore; D012243:Rhodopsin