Imaging bacteriorhodopsin-like molecules of claret-membranes from Tibet halobacteria xz515 by atomic force microscope

Halobacteria H.sp.xz 515 was isolated from a salt lake in Tibet. Although p roton release-and-uptake across claret membrane is in reverse order compare d to bacteriorhodopsin in purple membrane from Halobacterium Sali-narum, an d its efficiency of proton pump is much lower, AFM image shows that the mol ecules are still arranged in a two-dimensional hexagonal lattice of trimers . Primary structure of C- to G-helix of the archaerhodopsin shows that it h as only 56% homology with bacteriorhodopsin. But the interactive amino acid residues at the interface between Band D-helixes are conserved. These amin o acid residues are believed to play a significant role in the stability of protein oligomers.