Vibrational spectroscopy of bacteriorhodopsin mutants: Evidence for the interaction of proline-186 with the retinylidene chromophore

Journal Article · Tue Jun 26 00:00:00 EDT 1990 · Biochemistry; (USA)

DOI:https://doi.org/10.1021/bi00477a011· OSTI ID:6532469

Rothschild, K J; He, Y W; Mogi, T; Marti, T; Stern, L J; Khorana, H G ^[1]

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1. Boston Univ., MA (USA)

Fourier-transform infrared difference spectroscopy has been used to study the role of the three membrane-embedded proline residues, Pro-50, Pro-91, and Pro-186, in the structure and function of bacteriorhodopsin. All three prolines were replaced by alanine and glycine; in addition, Pro-186 was changed to valine. Difference spectra were recorded for the bR----K and bR----M photoreactions of each of these mutants and compared to those of wild-type bacteriorhodopsin. Only substitutions of Pro-186 caused significant perturbations in the frequency of the C = C and C - C stretching modes of the retinylidene chromophore. In addition, these substitutions reduced bands in the amide I and II region associated with secondary structural changes and altered signals assigned to the adjacent Tyr-185. Pro-186----Val caused the largest alterations, producing a second species similar to bR548 and nearly blocking chromophore isomerization at 78 K but not at 250 K. These results are consistent with a model of the retinal binding site in which Pro-186 and Tyr-185 are located in direct proximity to the chromophore and may be involved in linking chromophore isomerization to protein structural changes. Evidence is also found that Pro-50 may be structurally active during the bR----K transition and that substitution of this residue by glycine preserves the normal protein structural changes during the photocycle.

• OSTI ID: 6532469
• Journal Information: Biochemistry; (USA), Vol. 29:25; ISSN 0006-2960
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
PROLINE
BIOLOGICAL FUNCTIONS
RHODOPSIN
MOLECULAR STRUCTURE
ALANINES
FOURIER ANALYSIS
FOURIER TRANSFORM SPECTROMETERS
GLYCINE
INFRARED SPECTRA
MUTANTS
RETINA
SCHIFF BASES
ULTRASTRUCTURAL CHANGES
VALINE
AMINES
AMINO ACIDS
AZOLES
BODY
BODY AREAS
CARBOXYLIC ACIDS
EYES
FACE
FUNCTIONS
HEAD
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
IMINES
MEASURING INSTRUMENTS
MORPHOLOGICAL CHANGES
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANS
PIGMENTS
PROTEINS
PYRROLES
PYRROLIDINES
SENSE ORGANS
SPECTRA
SPECTROMETERS
550200* - Biochemistry