Bacteriorhodopsin is the one of the best-studied models of an ion pump. Five atomic models are now available, yet their comparison reveals differences of some loops connecting the seven transmembrane alpha-helices. In an attempt to resolve this enigma, topographs were recorded in aqueous solution with the atomic force microscope (AFM) to reveal the most native surface structure of bacteriorhodo...

The purple membrane ofHalobacterium halobium contains a single protein known as bacteriorhodopsin, which is composed of 1 mol retinal]mol bacterio-opsin [ 1 ]. The organization of the protein within each purple membrane sheet is that of an exact 2-dimensional crystal. X-ray and electron diffraction data have revealed that the bacteriorhodopsin in purple membrane is arranged as trimeric units in...

We have studied opto-electric properties of wild type bacteriorhodopsin and its two artificial variants. We have measured opto-electric responses with respect to wavelength for all three proteins and we describe the use of the proteins for color detection. Opto-electric responses of proteins to set of colored lights were measured and it has been shown that bacteriorhodopsin and its variants can...

Delipidated bacteriorhodopsin has been reconstituted with endogenous polar lipids from Halobacterium halobium. The vesicle (diameter, 250-500 A) formed are very stable, relatively homogeneous in bacteriorhodopsin and lipid content, and almost optically clear; a minor turbid fraction can be separated by gel filtration. Bacteriorhodopsin in the reconstituted vesicles has an inside out orientation...

Structural changes are central to the mechanism of light-driven proton transport by bacteriorhodopsin, a seven-helix membrane protein. The main intermediate formed upon light absorption is M, which occurs between the proton release and uptake steps of the photocycle. To investigate the structure of the M intermediate, we have carried out electron diffraction studies with two-dimensional crystal...

On page 255 of this issue, Luecke et al. (1) reveal the structure of bacteriorhodopsin, an active transport protein, frozen in midstroke. Bacteriorhodopsin is a membrane protein that uses a photon of visible light as an energy source to transport a proton across the membrane against an electrochemical gradient, resulting in proton release on one side of the membrane and proton uptake on the opp...

Fourier transform infrared difference spectroscopy has been used to obtain the vibrational modes in the chromophore and apoprotein that change in intensity or position between light-adapted bacteriorhodopsin and the K and M intermediates in its photocycle and between dark-adapted and light-adapted bacteriorhodopsin. Our infrared measurements provide independent verification of resonance Raman r...

Bacteriorhodopsin, a light activated protein that creates a proton gradient in halobacteria, has long served as a simple model of proton pumps. Within bacteriorhodopsin, several key sites undergo protonation changes during the photocycle, moving protons from the higher pH cytoplasm to the lower pH extracellular side. The mechanism underlying the long-range proton translocation between the centr...

Halobacterium halobium spheroplasts synthesize and accumulate a bacteriorhodopsin precursor. By labeling of the precursor with [35S]Met and [3H]Leu followed by Edman degradation, we have confirmed the previous conclusion from the DNA sequencing that the precursor contains 13 additional amino acids at the NH2 terminus of bacteriorhodopsin. Although not processed in the spheroplasts, it integrate...

A photodiode array in conjunction with a rapid stopped-flow mixing method, with a millisecond time resolution, is used here to study the refolding of the membrane protein bacteriorhodopsin from an apoprotein state with a native-like secondary structure in mixed phospholipid/detergent micelles. Refolding to the native state is initiated by the rapid mixing of all-trans-retinal and the apoprotein...