C14-C15 single bond isomerizations of the retinal chromophore involved in the proton-pumping mechanism of bacteriorhodopsin

Journal Article · Fri Jan 31 23:00:00 EST 1986 · Proc. Natl. Acad. Sci. U.S.A.; (United States)

DOI:https://doi.org/10.1073/pnas.83.4.967· OSTI ID:6436476

Smith, S O; Hornung, I; van der Steen, R; Pardoen, J A; Braiman, M S; Lugtenburg, J; Mathies, R A

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
• OSTI ID: 6436476
• Journal Information: Proc. Natl. Acad. Sci. U.S.A.; (United States), Journal Name: Proc. Natl. Acad. Sci. U.S.A.; (United States) Vol. 83:4; ISSN PNASA
• Country of Publication: United States
• Language: English

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59 BASIC BIOLOGICAL SCIENCES
BIOSYNTHESIS
BODY
BODY AREAS
CARBON 13
CARBON ISOTOPES
CHEMICAL BONDS
CHEMICAL REACTIONS
DEUTERIUM
EVEN-ODD NUCLEI
EYES
FACE
HEAD
HYDROGEN ISOTOPES
ISOMERIZATION
ISOTOPES
LABELLING
LASER SPECTROSCOPY
LIGHT NUCLEI
LOW TEMPERATURE
NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANS
PHOTOSYNTHETIC BACTERIA
PIGMENTS
PROTEINS
RAMAN SPECTROSCOPY
RETINA
RHODOPSIN
SENSE ORGANS
SPECTROSCOPY
STABLE ISOTOPES
SYNTHESIS