STRUCTURE OF HYPSORHODOPSIN: ANALYSIS BY FOURIER TRANSFORM INFRARED SPECTROSCOPY AT 10 K |
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| Authors: | Jun Sasaki Akio Maeda Yoshinori Shichida Michel Groesbeek Johan Lugtenburg Tôru Yoshizawa |
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| Institution: | Department of Biophysics, Faculty of Science, Kyoto University, Kyoto 606–1, Japan;Chemistry Department, Gorlaeus Laboratories, Leiden University, Leiden, The Netherlands;Department of Applied Physics and Chemistry, The University of Electro-Communications, 1–5–1 Chofugaoka, Chofu, Tokyo 182, Japan |
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| Abstract: | Abstract— Vibrational bands of hypsorhodopsin in the difference Fourier transform infrared spectra were identified as the bands which arose after formation of isorhodopsin by successive irradiations of bovine rhodopsin at 10 K with >500 nm light, and also as the bands disappeared upon conversion to bathorhodopsin by warming. The chromophore bands were assigned by the bands which shifted upon deuterium substitution of the polyene chain of the retinylidene chromophore. The presence of chromophore bands which shift by D2O exchange clearly shows that the Schiff base chromophore of hypsorhodopsin is protonated. The amide I bands and several other protein bands of hypsorhodopsin appeared at the same frequencies as those of bathorhodopsin, but they are different from those of rhodopsin and isorhodopsin. Furthermore, like bathorhodopsin, hypsorhodopsin displays the Cl—H out-of-plane bending mode which is weakly coupled with C12--–H out-of-plane mode. These facts show that hypsorhodopsin has a chromophore conformation and chromophore-opsin interaction more similar to bathorhodopsin than to rhodopsin and isorhodopsin. |
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