The structure of [Val']gramladm A mcorporated mto sodmm dodecyl-dz, sulphdte mlcelles has been studied by two-dlmenslonal proton NMR spectroscopy Analysis of nuclear Overhauser effects, spm-spm couphngs and solvent accesslblhty of NH groups show that the conformation of the Na+ complex of gramlcldm A m detergent mzelles. which In many ways mlmlc the phosphohpld bllayer of blomembranes, IS an N-terminal to N-termmal (head-to-head) dlmer ??f6L)D% LD 6 3 formed by two right-handed, single-stranded p" ' hehces with 6 3 residues per turn, dtffermg from Urry's structure by hdndedness of the hehces

Rhodopsin structure Bacteriorhodopsin structure Photoreception Light transformation Integral membrane protein RetinalPhotoreception and light transformation by living systems undoubtedly belong to the most surprising natural phenomena. Along with low-M, chromophoric compounds, specific proteins play an important part in absorption and transduction of light energy. Among photosensitive proteins, rhodopsin occupies a key position. This chromoprotein, with 1 l-c&retinal as a photoreceptor antenna, is the basis of the vision process in animals. For a long time all attempts to isolate rhodopsin from the photosensitive disc membranes in an individual and active state were not a success. The preparations obtained with various detergents were unsuitable for detailed structural analysis. Though dozens of laboratories actively participated in investigations of rhodopsin function and its structure peculiarities [l-6], the progress was rather slow. gradient of H+ turned out to be a universal energetic source for the cell. Interestingly, full protonpumping activity has been restored after complete delipidation and following reconstitution of bacteriorhodopsin into liposomes [ 16-l 81.The following discovery, seemingly bearing no direct relation to visual excitation, gave a new impetus to these investigations. Halophilic bacteria inhabiting salt lakes and solonchaks were found to contain a rhodopsin-like protein. This chromoprotein, bacteriorhodopsin, has a retinal residue in all-truns or 13-cis configuration as a light-sensitive system [7]. Its investigation developed rapidly into the field of membrane proteins. Proteins halorhodopsin and pigment PS-370, which contain retinal as the chromophore, have also been discovered [8-111.Bacteriorhodopsin was the first integral membrane protein the structure of which was elucidated. Henderson and Unwin, in their pioneering work, established by an electron diffraction technique that the bacteriorhodopsin polypeptide chain is composed of 7 a-helical rods spanning the membrane [ 191. Amino acid sequence of bacteriorhodopsin was elucidated in our laboratory (using unidentified strain and H. halobium RI), and the first model for the polypeptide chain arrangement in the membrane was proposed [20,21]. The regions of polypeptide loops connecting the helices, along with the N-and C-terminal fragments exposed at the membrane surface were determined by limited proteolysis. One year later similar results on bacteriorhodopsin primary structure were obtained by Khorana et al.: working apparently with the strain S-9 Halobacterium halobium they found an additional tryptophan residue in position 137 and a few substitutions in comparison with our data. Thus it was established that the bacteriorhodopsin polypeptide chain 'consists of 248 amino acid residues [22,23]. Our recent results agree with these data. Bacteriorhodopsin plays the role of a solar battery, very important for the vital activity of bacteria [12]. Rapid progress was achieved in the elucidation of bacteriorhodopsin functioning as a ligh...

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Covalent coupling of bovine rhodopsin to CPG-thiol glass was used for separation of CNBr peptides. It is shown that cysteine residues 322 and 323 in the C-terminal cytoplasmic fragment of rhodopsin are modified with palmitic acid.

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