Biophysical Journal 45: 985-992 (1984)
© 1984 the Biophysical Society

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Groma, G I Articles by Stoeckenius, W Search for Related Content PubMed PubMed Citation Articles by Groma, G I Articles by Stoeckenius, W

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.

ABSTRACT

The cell membrane of Halobacterium halobium (H. 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 on Ficoll/NaCl/CsCl density gradients. Under continuous illumination (550 +/- 50 nm) varied from 0 to 40 mW cm-2, the vesicles maintain a membrane potential of 0 to -100 mV. The membrane potential was measured by flow dialysis of 3H-TPMP+ 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.

This article has been cited by other articles:

				L. Rivas, S. Hippler-Mreyen, M. Engelhard, and P. Hildebrandt Electric-Field Dependent Decays of Two Spectroscopically Different M-States of Photosensory Rhodopsin II from Natronobacterium pharaonis Biophys. J., June 1, 2003; 84(6): 3864 - 3873. [Abstract] [Full Text] [PDF]