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Tryptophan perturbation in the L intermediate of bacteriorhodopsin: fourier transform infrared analysis with
A Maeda1, J Sasaki, Y J Ohkita
1Department of Biophysics, Faculty of Science, Kyoto University, Japan.
Abstract:
In the photoreaction of bacteriorhodopsin, the L intermediate shows an intense band at 3486 cm-1 which is unaffected by 2H2O (Maeda, A., Sasaki, J., Shichida, Y., & Yoshizawa, T. (1992) Biochemistry 31, 462-467]. This band is shifted to 3477 cm-1 by [indole-15N]tryptophan substitution and therefore is assigned to the N-H stretching vibration of the indole of tryptophan. Free indole in carbon tetrachloride shows its N-H stretching vibration at 3491 cm-1 [Fuson, N., Josien, M.-L., Powell, R. L., & Utterback, E. (1952) J. Chem. Phys. 20, 145-152]. Thus, it is suggested that at least one tryptophan residue in the L intermediate is not hydrogen bonded.