Coupling between the bacteriorhodopsin photocycle and the protonmotive force in halobacterium halobium cell envelope vesicles. II. Quantitation and preliminary modeling of the M. -->. bR reactions. [Halobacterium halobium]

Journal Article · Tue May 01 04:00:00 EDT 1984 · Biophys. J.; (United States)

DOI:https://doi.org/10.1016/S0006-3495(84)84243-5· OSTI ID:5864016

Groma, G I; Helgerson, S L; Wolber, P K; Beece, D; Dancshazy, Z; Keszthelyi, L; Stoeckenius, W

The cell membrane of Halobacterium halobium contains the proton-pump bacteriorhodopsin, which generates a light-driven transmembrane protonmotive force. The interaction of the bacteriorhodopsin photocycle with the electric potential component of the protonmotive force has been investigated. H. halobium cell envelope vesicles have been prepared by sonication and further purified by ultracentrifugation of Ficoll/NaCl/CsCl density gradients. Under continuous illumination (550 +/- 50 nm) varied from 0 to 40 mW cm/sup -2/, the vesicles maintain a membrane potential of 1 to -100 mV. The membrane potential was measured by flow dialysis of /sup 3/H-TPMP/sup +/ uptake and could be abolished by the uncoupler carbonylcyanide-m-chlorophenylhydrazone. Time-resolved absorption spectroscopy was used to measure the decay kinetics of the M photocycle intermediate, which was initiated by a weak laser flash (588 nm), while the vesicles were continuously illuminated as above. The M decay kinetics were fitted with two exponential decays by a computer deconvolution program. The faster decaying form decreases in amplitude (70 to 10% of the total) and the slower decaying form increases in amplitude and lifetime (23 to 42 ms) as the background light intensity increases. Although any correlation between the membrane potential and the bacteriorhodopsin photocycle M-forms is complex, the present data will allow specific tests of the physical mechanism for this interaction to be designed and conducted.

• Research Organization: Univ. of California, San Francisco
• OSTI ID: 5864016
• Journal Information: Biophys. J.; (United States), Journal Name: Biophys. J.; (United States) Vol. 45:4; ISSN BIOJA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
BIOCHEMICAL REACTION KINETICS
BIOLOGICAL PATHWAYS
CELL CONSTITUENTS
CELL MEMBRANES
CHEMICAL PREPARATION
CHEMICAL REACTIONS
DECOUPLING
ELECTRIC CHARGES
HYDRAZONES
ISOTOPE APPLICATIONS
KINETICS
LABELLED COMPOUNDS
MEMBRANES
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOSYNTHETIC BACTERIA
PHOTOSYNTHETIC MEMBRANES
PIGMENTS
PROTEINS
REACTION KINETICS
RHODOPSIN
SYNTHESIS
TRACER TECHNIQUES
TRITIUM COMPOUNDS