Abstract
AbstractBacteriorhodopsin is a seven-helix light-driven proton-pump that was structurally and functionally extensively studied. Despite a wealth of data, the single molecule kinetics of the reaction cycle remain unknown. Here, we use high-speed atomic force microscopy methods to characterize the single molecule kinetics of wild-type bR exposed to continuous light and short pulses. Monitoring bR conformational changes with millisecond temporal resolution, we determine that the cytoplasmic gate opens 2.9 ms after photon absorption, and stays open for proton capture for 13.2 ms. Surprisingly, a previously active protomer cannot be reactivated for another 37.6 ms, even under excess continuous light, giving a single molecule reaction cycle of ~20 s−1. The reaction cycle slows at low light where the closed state is prolonged, and at basic or acidic pH where the open state is extended.
Funder
Fundación Ramón Areces
U.S. Department of Health & Human Services | NIH | National Center for Complementary and Integrative Health
U.S. Department of Health & Human Services | NIH | National Institute of Neurological Disorders and Stroke
Publisher
Springer Science and Business Media LLC
Subject
General Physics and Astronomy,General Biochemistry, Genetics and Molecular Biology,General Chemistry
Cited by
21 articles.
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