Investigation of the primary photochemistry of bacterio rhod opsin by low temperature fourier transform ir spectroscopy

Siebert, F.; Maentele, W.

European Journal of Biochemistry 130(3): 565-574


ISSN/ISBN: 0014-2956
Accession: 005748215

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The method of Fourier-transform IR difference spectroscopy was applied to investigate the transition at K of bacteriorhodopsin in its light-adapted form to K610, the first intermediate which is stable at low temperature. In addition to unmodified bacteriorhodopsin, bacteriorhodopsin in 2H2O and bacteriorhodopsin containing [15-2H]retinal was used. Major rearrangements occur in the Schiff base in this transition. It is not possible to identify a C = N stretching vibration of the Schiff base in K610. The identification of an N-H bending vibration in K610 shows that the N of the previous Schiff base still has a proton attached. The fingerprint region exhibits very unusual features for K610 and bears no similarity to protonated retinylidene Schiff base model compounds of any isomeric composition. No conclusions on the isomeric state of the retinal in K610 can be drawn. The spectra show that the terminal part of the retinal is predominantly reflected in the difference spectra. This indicates that the most polar part of the retinal is located near the Schiff base. Protein molecular changes apparently occur in this transition at K.