The parallel model for the bacteriorhodopsin (BR) photocycle at neutral pH and a temperature near 20 degrees C contains an M-fast cycle with steps BR-->K-->L-->Mf-->N-->O-->BR and an M-slow cycle which contains steps BR-->K-->L-->Ms-->BR. With increasing actinic laser strength, the M-fast cycle at first rises faster than the M-slow cycle, but reaches saturation sooner and at a lower level than ...

Sensory rhodopsin I (SR-I) and bacteriorhodopsin (BR) from Halobacterium halobium show broad structural and spectroscopic similarities and yet perform distinct functions: photosensory reception and proton pumping, respectively. Probing the photoactive sites of SR-I and BR with 24 retinal analogs reveals differences in the protein environments near the retinal 13-methyl group and near the beta-i...

Differential scanning calorimetry and Fourier-transform infrared spectroscopy have been used to characterize the thermal stability of bacteriorhodopsin (BR) cleaved within different loops connecting the helical rods. The results are compared to those of the native protein. We show that the denaturation temperature and enthalpy of BR cleaved at peptide bond 71-72 or 155-156 are lower than those ...

Amphipols (APols) are specially designed amphipathic polymers that stabilize membrane proteins (MPs) in aqueous solutions in the absence of detergent. A8-35, a polyacrylate-based APol, has been grafted with an oligodeoxynucleotide (ODN). The synthesis, purification and properties of the resulting 'OligAPol' have been investigated. Grafting was performed by reacting an ODN carrying an amine-term...

Bacteriorhodopsin (bR) is a retinal protein in purple membrane of Halobacterium salinarum, which functions as a light-driven proton pump. We have detected pressure-induced isomerization of retinal in bR by analyzing 15N cross polarization-magic angle spinning (CP-MAS) NMR spectra of [zeta-15N]Lys-labeled bR. In the 15N-NMR spectra, both all-trans and 13-cis retinal configurations have been obse...

Bacteriorhodopsin (bR) is a light-driven proton pump, which is a membrane protein with seven transmembrane helices and a prosthetic group of retinal. The structure of bR has been determined at high resolution, and the homology modeling of G-protein coupled receptors, which have seven transmembrane helices, is usually carried out based on the structure of bR as the structure template. However, t...

We are testing a strategy for creating three-dimensional crystals of integral membrane proteins which involves the addition of a large soluble domain to the membrane protein to provide crystallization contacts. As a test of this strategy we designed a fusion between the membrane protein bacteriorhodopsin (BR) and the catalytic subunit of aspartyl transcarbamylase from Escherichia coli. The fusi...

The light-driven proton pump bacteriorhodopsin (bR) is a transmembrane protein that uses large conformational changes for proton transfer from the cytoplasmic to the extracellular regions. Crystal structures, due to their solvent conditions, do not resolve the effect of lipid molecules on these protein conformational changes. To begin to understand the molecular details behind such large confor...

The retinal chromophore of bacteriorhodopsin is attached as a Schiff's base with the epsilon-amino group of a lysine residue. The site of attachment has now been investigated by the use of resonance Raman spectroscopy which has previously been shown to be sensitive to 15N isotope substitution at the Schiff's base. Bacteriorhodopsin samples obtained from bacteria grown in a medium containing eit...

This work demonstrates the integration of the energy-transducing proteins bacteriorhodopsin (BR) from Halobacterium halobium and cytochrome c oxidase (COX) from Rhodobacter sphaeroides into block copolymeric vesicles towards the demonstration of coupled protein functionality. An ABA triblock copolymer-based biomimetic membrane possessing UV-curable acrylate endgroups was synthesized to serve as...