Perturbation effects on the observed deprotonation processes in the photocycle of bacteriorhodopsin

Technical Report · Tue Jan 01 04:00:00 EST 1985

OSTI ID:5658966

Dupuis, P; El-Sayed, M A

The kinetics of formation of both M/sub 412/ (from its absorption at 405 nm) and the tyrosinate ion (from its absorption at 297 nm) during the photocycle of bacteriorhodopsin are studied simultaneously under different types of perturbation: pH, temperature, high concentrations of salt and deionization. Two formation rates are observed for M/sub 412/. The slow one is dominant under physiological conditions and is found to be slightly faster than that for the tyrosinate formation. This does not agree with a previous proposal that the tyrosinate formation is a prerequisite to the M/sub 412/ formation. The absorption change at 297 nm is also monitored for the deionized and acidified bacteriorhodopsins (blue membranes). For these samples, only the trans-cis isomerization of retinal is present. The tyrosine deprotonation is not observed. The addition of different salts to the deionized membrane restores the original color and causes a tyrosine deprotonation during the photocycle. A model is proposed to account for the observed deprotonation processes in the photocycle of bacteriorhodopsin. High concentrations of salt do not increase the rates of deprotonation of the protonated Schiff base and tyrosine nor do they increase the relative amplitude of the fast component of the Schiff base deprotonation. This strongly suggests that the observed gain in the quantum yield of proton release per M/sub 412/ formed when the salt concentration is increased is not a result of an increase in these rates. 47 refs., 3 figs.

• Research Organization: California Univ., Los Angeles (USA). Dept. of Chemistry and Biochemistry
• DOE Contract Number: AS03-78ER70278
• OSTI ID: 5658966
• Report Number(s): UCLA-34P278-49; ON: DE85015576
• 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
BACTERIA
CHEMISTRY
DISPERSIONS
HYPERTONIC SOLUTIONS
MICROORGANISMS
MIXTURES
ORGANIC COMPOUNDS
PH VALUE
PHOTOCHEMISTRY
PIGMENTS
PROTEINS
RHODOPSIN
SOLUTIONS
TEMPERATURE DEPENDENCE