Transmembrane location of retinal in bacteriorhodopsin by neutron diffraction

Journal Article · Tue May 22 04:00:00 EDT 1990 · Biochemistry; (USA)

DOI:https://doi.org/10.1021/bi00472a022· OSTI ID:6649784

Hauss, T; Grzesiek, S; Otto, H; Westerhausen, J; Heyn, M P ^[1]

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1. Freie Universitaet Berlin (Germany, F.R.)

The transmembrane location of the chromophore of bacteriorhodopsin was obtained by neutron diffraction on oriented stacks of purple membranes. Two selectively deuterated retinals were synthesized and incorporated in bacteriorhodopsin by using the retinal- mutant JW5: retinal-d11 (D11) contained 11 deuterons in the cyclohexene ring, and retinal-d5 (D5) had 5 deuterons as close as possible to the Schiff base end of the chromophore. The membrane stacks had a lamellar spacing of 53.1 A at 86% relative humidity. Five orders were observed in the lamellar diffraction pattern of the D11, D5, and nondeuterated reference samples. The reflections were phased by D2O-H2O exchange. The absolute values of the structure factors were nonlinear functions of the D2O content, suggesting that the coherently scattering domains consisted of asymmetric membrane stacks. The centers of deuteration were determined from the observed intensity differences between labeled and unlabeled samples by using model calculations and Fourier difference methods. With the origin of the coordinate system defined midway between consecutive intermembrane water layers, the coordinates of the center of deuteration of the D11 and D5 label are 10.5 +/- 1.2 and 3.8 +/- 1.5 A, respectively. Alternatively, the label distance may be measured from the nearest membrane surface as defined by the maximum in the neutron scattering length density at the water/membrane interface. With respect to this point, the D11 and D5 labels are located at a depth of 9.9 +/- 1.2 and 16.6 +/- 1.5 A, respectively. The chromophore is tilted with the Schiff base near the middle of the membrane and the ring closer to the membrane surface. The vector connecting the two label positions in the chromophore makes an angle of 40 +/- 12 degrees with the plane of the membrane.

• OSTI ID: 6649784
• Journal Information: Biochemistry; (USA), Journal Name: Biochemistry; (USA) Vol. 29:20; ISSN 0006-2960; ISSN BICHA
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
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Photobiological
& Thermochemical Conversion-- (1980-)
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59 BASIC BIOLOGICAL SCIENCES
CARBOXYLIC ACID ESTERS
CELL CONSTITUENTS
CELL MEMBRANES
CHEMICAL REACTIONS
COHERENT SCATTERING
DEUTERATION
DEUTERIUM
DIFFRACTION
ESTERS
HYDROGEN ISOTOPES
IMINES
ISOTOPE APPLICATIONS
ISOTOPES
LIGHT NUCLEI
MEMBRANES
MOLECULAR STRUCTURE
NEUTRON DIFFRACTION
NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHOTOSYNTHETIC MEMBRANES
PIGMENTS
PROTEINS
RETINOIC ACID
RHODOPSIN
SCATTERING
SCHIFF BASES
STABLE ISOTOPES
TRACER TECHNIQUES