Correlation between proton pumping and the bacteriorhodopsin photocycle

Journal Article · Wed Oct 31 23:00:00 EST 1984 · Proc. Natl. Acad. Sci. U.S.A.; (United States)

DOI:https://doi.org/10.1073/pnas.81.22.7079· OSTI ID:5871099

Li, Q; Govindjee, R; Ebrey, T G

In an attempt to establish a relationship between proton pumping and the photocycle intermediates of bacteriorhodopsin, we have studied the effects of pH and temperature of flash-induced proton pumping and the photointermediates O/sub 640/ and M/sub 412/. The relative quantum yield of flash-induced proton pumping is both pH and temperature dependent. It is high in the acid pH range and at low temperatures but decreases in the basic pH range and at high temperatures. The decay of M/sub 412/ is biphasic. The amplitude of the slowly decaying component (M/sup s/) was found to be pH dependent with a pK similar to that of the ..delta..pH. The pH dependence of the fast-decaying component (M/sup f/) is opposite to that of M/sup s/ and ..delta..pH. Like that of M/sup s/, the amplitude of O/sub 640/ is high in the acid pH range, but unlike the amplitude of M/sup s/, it declines very rapidly at pHs greater than 6.5; the amplitude of O/sub 640/ becomes zero around pH 8. The temperature dependence of the amplitude of M/sup s/ was found to be similar to that of ..delta..pH, being high at low temperatures and low in the high-temperature range. The temperature dependence of M/sup f/ and O/sub 640/ is opposite to that of ..delta..pH and M/sup s/. Whereas, O/sub 640/ and M/sup s/ seem to be likely candidates (from the pH dependence) for coupling between proton pumping and the photocycle, M/sup s/ is more likely because (i) the relative quantum yield of both M/sup s/ and ..delta..pH seem not to go to zero at higher pHs and (ii) M/sup s/ and ..delta..pH have similar temperature dependence. 26 references, 4 figures.

• Research Organization: Univ. of Illinois, Urbana
• DOE Contract Number: AC02-82ER12087
• OSTI ID: 5871099
• Journal Information: Proc. Natl. Acad. Sci. U.S.A.; (United States), Journal Name: Proc. Natl. Acad. Sci. U.S.A.; (United States) Vol. 81:22; ISSN PNASA
• Country of Publication: United States
• Language: English

Related Subjects

550500* -- Metabolism
59 BASIC BIOLOGICAL SCIENCES
BARYONS
BIOCHEMICAL REACTION KINETICS
BIOCHEMISTRY
CELL CONSTITUENTS
CELL MEMBRANES
CHEMICAL REACTIONS
CHEMISTRY
ELEMENTARY PARTICLES
FERMIONS
HADRONS
KINETICS
MEMBRANE TRANSPORT
MEMBRANES
NUCLEONS
ORGANIC COMPOUNDS
PH VALUE
PHOTOCHEMICAL REACTIONS
PHOTOSYNTHESIS
PIGMENTS
PROTEINS
PROTONS
REACTION KINETICS
RHODOPSIN
SYNTHESIS
TEMPERATURE EFFECTS