Resonance Raman Examination of the Wavelength Regulation Mechanism in Human Visual Pigments
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- 作者：Gerd G. Kochendoerfer ; Zhiyan Wang ; Daniel D. Oprian ; and Richard A. Mathies
- 刊名：Biochemistry
- 出版年：1997
- 出版时间：June 3, 1997
- 年：1997
- 卷：36
- 期：22
- 页码：6577 - 6587
- 全文大小：378K
- 年卷期：v.36,no.22(June 3, 1997)
- ISSN：1520-4995
文摘
Resonance Raman spectra of recombinant human green andred cone pigments have beenobtained to examine the molecular mechanism of color recognition byvisual pigments. Spectra wereacquired using a 77 K resonance Raman microprobe or preresonance Ramanspectroscopy. The vibrationalbands were assigned by comparison to the spectra of bovine rhodopsinand model compounds. The C=NHstretching frequencies of rhodopsin, the green cone pigment, and thered cone pigment in H2O (D2O) arefound at 1656 (1623), 1640 (1618), and 1644cm-1, respectively. Together withprevious resonanceRaman studies on iodopsin [Lin, S. W., Imamoto, Y., Fukada, Y.,Shichida, Y., Yoshizawa, T., & Mathies,R. A. (1994) Biochemistry 33, 2151-2160], these valuessuggest that red and green pigments have verysimilar Schiff base environments, while the Schiff base group inrhodopsin is more strongly hydrogen-bonded to its protein environment. The absence of significantfrequency and intensity differences ofmodes in the fingerprint and the hydrogen out-of-plane wagging regionsfor all these pigments does notsupport the hypothesis that local chromophore interactions with chargedprotein residues and/orchromophore planarization are crucial for the absorption differencesamong these pigments. However,our data are consistent with the idea that the Schiff base group inblue visual pigments is stabilized byprotein and water dipoles and that the removal of this dipolar fieldshifts the absorption maximum fromblue to green. A further red shift of the 
max fromthe green to the red pigment is successfully modeledby the addition of hydroxyl-bearing amino acids (Ser164,Tyr261, and Thr269) close to the ionone ringthatlower the transition energy by interacting with the change of dipolemoment of the chromophore uponexcitation. The increased hydrogen bonding of the protonatedSchiff base group in rhodopsin is predictedto account for the 30 nm blue shift of its absorption maximum comparedto that of the green pigment.
max fromthe green to the red pigment is successfully modeledby the addition of hydroxyl-bearing amino acids (Ser164,Tyr261, and Thr269) close to the ionone ringthatlower the transition energy by interacting with the change of dipolemoment of the chromophore uponexcitation. The increased hydrogen bonding of the protonatedSchiff base group in rhodopsin is predictedto account for the 30 nm blue shift of its absorption maximum comparedto that of the green pigment.