Design of a helix-bundle cross-link: NMR and UV-visible spectroscopic analyses and molecular modeling of ring-oxidized retinals

Journal Article · Tue Mar 19 00:00:00 EST 1991 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00225a035· OSTI ID:5078336

Williams, T C; Mani, V ^[1]

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1. Medical Univ. of South Carolina, Charleston (United States) M and S Data Analysis and Molecular Speculations, Charleston, SC (United States)

In order to generate potential chemical cross-links for studying the chromophore binding site of bacteriorhodopsin and related helix-bundle proteins, MnO{sub 2} was used to oxidize all-trans-retinal's ring moiety. The structures and solution conformations of three ring-oxidized retinal analogues have been determined by using UV-visible absorption and {sup 1}H and {sup 13}C NMR spectroscopies, primarily with regard to (i) the introduction of a functional group at the ring end of the chromophore, (ii) the retention of the all-trans geometry of the polyenal side chain, and (iii) the torsional angle of the ring-polyenal bond. Analyses of their UV-visible absorption spectral parameters and NMR spectral parameters indicated the 4-oxo and the 2,3-dehydro-4-oxo derivatives both possess the twisted 6-2-cis conformation adopted by most six-membered ring analogues of retinal in solution or crystal. Because the chromophores of bacterio-and halorhodopsins and sensory rhodopsins are bound as the 6-s-trans conformer the authors suggest that the cyclopentenyl analogue's {alpha}-diketo function may be favorably positioned within the binding pocket and sufficiently reactive toward nucleophilic attack to cross-link an arginine located in or near the ring end of the chromophore cavity: Arg{sup 134} according to the current model of bacteriorhodopsin's tertiary structure of Arg{sup 82} as postulated from an alternate model constructed primarily to accommodate the external point charge contribution to bacteriorhodopsins's opsin shift.

• OSTI ID: 5078336
• Journal Information: Biochemistry; (United States), Vol. 30:11; ISSN 0006-2960
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
RETINOIC ACID
NUCLEAR MAGNETIC RESONANCE
RHODOPSIN
MOLECULAR MODELS
ARGININE
CARBON 13
GEOMETRY
PROTONS
ULTRAVIOLET SPECTRA
VISIBLE SPECTRA
AMINO ACIDS
BARYONS
CARBON ISOTOPES
CARBOXYLIC ACID ESTERS
CARBOXYLIC ACIDS
ELEMENTARY PARTICLES
ESTERS
EVEN-ODD NUCLEI
FERMIONS
HADRONS
ISOTOPES
LIGHT NUCLEI
MAGNETIC RESONANCE
MATHEMATICAL MODELS
MATHEMATICS
NUCLEI
NUCLEONS
ORGANIC ACIDS
ORGANIC COMPOUNDS
PIGMENTS
PROTEINS
RESONANCE
SPECTRA
STABLE ISOTOPES
550201* - Biochemistry- Tracer Techniques