• Bacteriorhodopsin

    measured on the SURFE2R N1


Target Synonyms and Classification: Bacteriorhodopsin (BR) belongs to the Ion-translocating Microbial Rhodopsin Family (MRF, TCDB: 3.E.1), which catalyzes light-driven ion translocation across microbial cytoplasmic membranes or serve as light receptors.

Function: BR provides a major source of energy: Using light energy it pumps protons across the membrane out of the cell and generates a proton gradient, which in turn is used to generate chemical energy in form of ATP through the action of the ATP-Synthase. Upon light absorption (λmax = 570 nm), the covalently bound cofactor Retinal undergoes a series of conformational transitions, which are coupled to the translocation of one proton. Proton translocation involves binding, intramolecular transfer, and release of a proton which requires – besides retinal – different amino acids. The whole photocycle takes about 15 ms.

Organism and Localization: Bacteriorhodopsin is used by Archaea, most notably by Haloarchaea like Halobacterium salinarum, an extremophile that occupies hypersaline lakes. BR forms two-dimensional crystalline patches known as the purple membrane, which can occupy up to 50 % of the surface area of the archaeal cell.

Substrates and Inhibitors: Proton translocation by BR is inhibited by blue light, which is known as the “blue light effect”. Blue light enables a shortcut within the photocycle which leads to uncoupling of light adsorption from H+ translocation. BR can be inactivated by mutation of the proton donor D96 to asparagine. The mutant can be reactivated using sodium azide, which essentially functions as a mobile proton donor.

Related Transporters: All Rhodopsins share the properties of a covalently bound retinal coupling light adsorption with ion translocation. There are several bacterial sensory Rhodopsins, such as the Cl- pumping Halorhodopsin, the Na+ pumping Rhodopsin KR2, Proteorhodopsin, which acts very similar to BR and Channelrhodopsin, which has a channel-like mechanism. Beside energy conversion they play key roles in phototaxis. Rhodopsins are also found in vertebrates, where they belong to the class of G protein-coupled receptors. Here, they are commonly found in light-sensing organs and responsible for the eyesight in humans.

Data and Applications

BR – pH dependence on the SURFE2R N1

BR pH dependence Slider

Icon N1   SURFE2R N1 data and applications:

Light induced currents have been measured at different pH values. Proton translocation depends on proton binding and release which show apparent pK values of > 10.5 and 4.9 respectively.

BR – different light intensities on the SURFE2R N1

BR Figure 2  intensity

Icon N1   SURFE2R N1 data and applications:

Light induced currents have been measured at different light intensities. The SURFE2R N1 SOLs standard green LED is able to satturate BR activity at ~ 100 mA.

BR – Action vs. Absorption Spectra on SURFE2R N1

BR Figure 2  wavelength

Icon N1   SURFE2R N1 data and applications:

Light induced currents have been measured using five LED sensor plates with different emission wavelengths. The wavelength dependent peak currents (action spectra) overlay with the absorption spectrum of BR


No tagged items found


2002 - Photocurrents Generated by Bacteriorhodopsin Adsorbed on Thiol/Lipid Bilayers Supported by Mercury

Icon N1   SURFE²R-technology (custom-built system) publication in Langmuir (2002)

Dolfi A., Tadini-Buoninsegni F., Moncelli M.R., Guidelli R.

1993 - Charge transport by ion translocating membrane proteins on solid supported membranes

Icon N1   SURFE²R-technology (custom-built system) publication in Biophysical Journal (1993)

Seifert K., Fendler K., Bamberg E.

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