Biomaterial Database

Light activates rotations of bacteriorhodopsin in the purple membrane. 1984

P L Ahl, and R A Cone

To investigate how a photoactivated chromophore drives the proton pump mechanism of bacteriorhodopsin, we have observed how the chromophore rotates during the photocyle. To do this, we examined the dichroism induced in aqueous suspensions of purple membrane fragments by flashes of linearly polarized light. We find that the flash stimulates both the photocycling chromophores and their noncycling neighbors to undergo large (greater than 10 degrees - 20 degrees) rotations within the membrane during the photocycle, and that these two chromophore populations undergo distinctly different sequences of rotations. All these rotations could be eliminated by glutaraldehyde fixation as well as by embedding unfixed fragments in polyacrylamide or agarose gels. Thus, in these immbolizing preparations the chromophore can photocycle without rotating inside a bacteriorhodopsin monomer by more than our detection limit of 2 degrees - 5 degrees. The large rotations we observed in aqueous suspensions of purple membranes were probably due to rotations of entire protein monomers. The process by which a photocycling monomer causes its noncycling neighbors to rotate may help explain the highly cooperative behavior bacteriorhodopsin exhibits when it is aggregated into crystalline arrays of trimers.

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D008027	Light	That portion of the electromagnetic spectrum in the visible, ultraviolet, and infrared range.	Light, Visible,Photoradiation,Radiation, Visible,Visible Radiation,Photoradiations,Radiations, Visible,Visible Light,Visible Radiations
D008433	Mathematics	The deductive study of shape, quantity, and dependence. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)	Mathematic
D008954	Models, Biological	Theoretical representations that simulate the behavior or activity of biological processes or diseases. For disease models in living animals, DISEASE MODELS, ANIMAL is available. Biological models include the use of mathematical equations, computers, and other electronic equipment.	Biological Model,Biological Models,Model, Biological,Models, Biologic,Biologic Model,Biologic Models,Model, Biologic
D002338	Carotenoids	The general name for a group of fat-soluble pigments found in green, yellow, and leafy vegetables, and yellow fruits. They are aliphatic hydrocarbons containing 4 terpene subunits.	Carotenes,Carotenoid,Tetraterpene Derivatives,Tetraterpenes,Carotene,Derivatives, Tetraterpene
D006217	Halobacterium	A genus of HALOBACTERIACEAE whose growth requires a high concentration of salt. Binary fission is by constriction.
D001436	Bacteriorhodopsins	Rhodopsins found in the PURPLE MEMBRANE of halophilic archaea such as HALOBACTERIUM HALOBIUM. Bacteriorhodopsins function as an energy transducers, converting light energy into electrochemical energy via PROTON PUMPS.	Bacteriorhodopsin
D013816	Thermodynamics	A rigorously mathematical analysis of energy relationships (heat, work, temperature, and equilibrium). It describes systems whose states are determined by thermal parameters, such as temperature, in addition to mechanical and electromagnetic parameters. (From Hawley's Condensed Chemical Dictionary, 12th ed)	Thermodynamic