High-sensitivity neutron diffraction of membranes: Location of the Schiff base end of the chromophore of bacteriorhodopsin

Journal Article · Fri Apr 01 04:00:00 EST 1988 · Proceedings of the National Academy of Sciences of the United States of America; (USA)

DOI:https://doi.org/10.1073/pnas.85.7.2146· OSTI ID:7101138

Heyn, M P; Westerhausen, J; Wallat, I; Seiff, F ^[1]

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1. Freie Universitaet Berlin (West Germany)

Three important events in the functional cycle of bacteriorhodopsin occur at the chromophore: the primary absorption of light, the isomerization from the all-trans to the 13-cis form, and the deprotonation and reprotonation of its Schiff base. The protonated Schiff base linkage of the chromophore with lysine-216 plays an essential role in the color regulation of the pigment and is most likely directly involved in the charge translocation of this light-driven proton pump. Although much is known about the structure of the protein, the position of this key functional group has not yet been determined. The authors have synthesized a retinal in which the five protons closest to the Schiff base are replaced by deuterons. The labeled retinal was spontaneously incorporated into bacteriorhodopsin by using a mutant of Halobacterium halobium that is deficient in the synthesis of retinal. The position of the labeled Schiff base end of the chromophore was determined in the two-dimensional projected density of dark-adapted bacteriorhodopsin by neutron diffraction. The result fits very well with their previous work using retinals that were selectively deuterated in the middle of the polyene chain or in the cyclohexene ring. A coherent structure emerges with the three labeled positions on one line, separated by distances that are in good agreement with the tilt angle of the polyene chain (about 20{degree}). The results show that it is possible to locate a small group containing as few as five deuterons in a membrane protein of molecular weight 27,000.

• OSTI ID: 7101138
• Journal Information: Proceedings of the National Academy of Sciences of the United States of America; (USA), Journal Name: Proceedings of the National Academy of Sciences of the United States of America; (USA) Vol. 85:7; ISSN 0027-8424; ISSN PNASA
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
140505 -- Solar Energy Conversion-- Photochemical
Photobiological
& Thermochemical Conversion-- (1980-)
550200* -- Biochemistry
59 BASIC BIOLOGICAL SCIENCES
AMINO ACIDS
BARYONS
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
COHERENT SCATTERING
DEUTERIUM COMPOUNDS
DIFFRACTION
ELEMENTARY PARTICLES
FERMIONS
HADRONS
HYDROGEN COMPOUNDS
IMINES
ISOMERIZATION
LYSINE
MAGNETIC RESONANCE
MEMBRANES
MOLECULAR STRUCTURE
NEUTRON DIFFRACTION
NUCLEAR MAGNETIC RESONANCE
NUCLEONS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHOTOSYNTHETIC BACTERIA
PHOTOSYNTHETIC MEMBRANES
PIGMENTS
PROTEINS
PROTONS
RESONANCE
RHODOPSIN
SCATTERING
SCHIFF BASES
VITAMIN A
VITAMINS