Steric constraint in the primary photoproduct of an archaeal rhodopsin from regiospecific perturbation of C-D stretching vibration of the retinyl chromophore.
In visual and archaeal rhodopsins, light energy is stored in the chromophore-protein interaction after retinal photoisomerization. This paper reports a novel method to monitor the steric constraint after retinal isomerization by use of enhanced C-D stretching vibrations. In the difference FTIR spectra between an archaeal light-sensor pharaonis phoborhodopsin (ppR) and the primary K intermediate at 77 K, no peaks were observed in the 2160-2330 cm-1 region for deuterated retinals at position 7, 8, 10, 11, 12, and 15, whereas a strong peak appeared at 2244 cm-1 for the K intermediate of ppR possessing a C14-D-labeled retinal. The 2244-cm-1 band is assigned as the C14-D stretching vibration, and enhanced absorption in the K state probably originates from the local steric constraint at the C14-D position (also possible electrostatic field effects) after the C13=C14 double bond rotation.
Sudo
Yuki
Y
Department of Materials Science and Engineering, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan.
Furutani
Yuji
Y
Wada
Akimori
A
Ito
Masayoshi
M
Kamo
Naoki
N
Kandori
Hideki
H
D015394:Molecular Structure; D010777:Photochemistry; D012172:Retinaldehyde / Q000737:chemistry* / Q000378:metabolism*; D025604:Rhodopsins, Microbial / Q000737:chemistry* / Q000378:metabolism*; D017550:Spectroscopy, Fourier Transform Infrared; D013237:Stereoisomerism; D014732:Vibration
D025604:Rhodopsins, Microbial; D012172:Retinaldehyde