Factors affecting the absorption maxima of acidic forms of bacteriorhodopsin. A study with artificial pigments

Journal Article · Fri Dec 01 04:00:00 EST 1989 · Biophysical Journal; (USA)

DOI:https://doi.org/10.1016/S0006-3495(89)82773-0· OSTI ID:6995445

Albeck, A; Friedman, N; Sheves, M; Ottolenghi, M ^[1]

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1. Weizmann Institute of Science, Rehovot (Israel)

The absorption maximum (568 nm) of light-adapted bacteriorhodopsin bR568 undergoes reversible changes after acidification. At pH 2.9, the absorption shifts to 605 nm (forming bR605) and it blue shifts to 565 nm, after further acidification to pH approximately 0.5 (forming bR565). Molecular models accounting for such acid-induced changes are relevant to the structure and function of bacteriorhodopsin. In the present study we approached the problem by applying artificial bR pigments based on selectively modified synthetic retinals. This may allow direct identification of the specific regions in the retinal binding site where the above changes in the protein-retinal interactions take place. We investigated the spectroscopic effects of acid in a variety of artificial pigments, including cyaninelike retinals, retinals bearing bulky groups at C4, short polyenes, and retinals in which the beta-ionone ring was substituted by aromatic rings. The results provide direct evidence for the hypothesis that the generation of bR605 is due to changes in polyene-opsin interactions in the vicinity of the Schiff base linkage. The second transition (to bR565) was not observed in artificial pigments bearing major changes in the ring structure of the retinal. Two approaches accounting for this observation are presented. One argues that the generation of bR565 is associated with acid-induced changes in retinal-protein interactions in the vicinity of the retinal ring. The second involves changes in polyene-opsin interactions in the vicinity of the Schiff base linkage.

• OSTI ID: 6995445
• Journal Information: Biophysical Journal; (USA), Journal Name: Biophysical Journal; (USA) Vol. 56:6; ISSN 0006-3495; ISSN BIOJA
• Country of Publication: United States
• Language: English

Related Subjects

550200* -- Biochemistry
59 BASIC BIOLOGICAL SCIENCES
ABSORPTION SPECTRA
CARBOXYLIC ACID ESTERS
ESTERS
IMINES
MEMBRANE PROTEINS
MOLECULAR STRUCTURE
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PH VALUE
PIGMENTS
PROTEINS
RECEPTORS
RETINOIC ACID
RHODOPSIN
SCHIFF BASES
SPECTRA
SPECTROPHOTOMETRY
STRUCTURE-ACTIVITY RELATIONSHIPS