C14-C15 single bond isomerizations of the retinal chromophore involved in the proton-pumping mechanism of bacteriorhodopsin
Resonance Raman spectroscopy is used to examine the possibility that C14-C15 single bond isomerizations of the retinal prosthetic group are involved in the photochemical reactions of bacteriorhodopsin. Normal mode calculations show that the vibration that contains predominantly C14-C15 stretch character is approx. = 70 cm lower in frequency in the 14-s-cis conformer than in the s-trans case. This geometric effect is insensitive to out-of-plane twists and should be observed in the sterically hindered 13-cis, 14-s-cis retinal protonated Schiff base, which has been proposed as the chromophore in the K and L intermediates of bacteriorhodopsin. Resonance Raman spectra were obtained of K625 by using the low temperature (77 K) spinning-cell technique. Isotopic substitutions with T and SH show that significant C14-C15 stretch character is observed in normal modes at approx. = 1185-1195 cm . The relatively high frequency of the C14-C15 stretch argues that K625 contains a 13-cis, 14-s-trans chromophore. Similarly, isotopic derivatives show that L550 has a localized C14-C15 stretch at 1172 cm , consistent with a 14-s-trans chromophore. These results argue that the primary step in bacteriorhodopsin is a C13=C14 trans cis photoisomerization that does not involve C14-C15 s-cis structures.
- Research Organization:
- Univ. of California, Berkeley, CA (United States)
- OSTI ID:
- 6436476
- Journal Information:
- Proc. Natl. Acad. Sci. U.S.A.; (United States), Vol. 83:4
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
59 BASIC BIOLOGICAL SCIENCES
CHEMICAL BONDS
ISOMERIZATION
RHODOPSIN
LABELLING
RAMAN SPECTROSCOPY
BIOSYNTHESIS
CARBON 13
DEUTERIUM
LOW TEMPERATURE
PHOTOSYNTHETIC BACTERIA
RETINA
BODY
BODY AREAS
CARBON ISOTOPES
CHEMICAL REACTIONS
EVEN-ODD NUCLEI
EYES
FACE
HEAD
HYDROGEN ISOTOPES
ISOTOPES
LASER SPECTROSCOPY
LIGHT NUCLEI
NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANS
PIGMENTS
PROTEINS
SENSE ORGANS
SPECTROSCOPY
STABLE ISOTOPES
SYNTHESIS
140505* - Solar Energy Conversion- Photochemical
Photobiological
& Thermochemical Conversion- (1980-)
550201 - Biochemistry- Tracer Techniques