紫膜の構造

概要

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The structure of the purple membrane is reviewed briefly. The purple membrane is the differentiated patch in the cell membrane of halobacteria which contains only one polypeptide, bacteriorhodopsin with a molecular weight of 26, 000. X-ray diffraction patterns demonstrated the presence of a two dimensional hexagonal lattice of the space group P3 in the purple membrane. The X-ray diffraction also indicates a high content of α-helix in the protein and the bilayer arrangement for the lipids. The three-dimensional structure of bacteriorhodopsin has been obtained at a resolution of 7Å from electron diffraction patterns and electron micrographs. One molecule conatins seven α-helical segments which pack neatly side by side and span the hydrophobic interior of the membrane. It is also described that reconstituted bacteriorhodopsin form the hexagonal lattice spontaneously in the isolated membrane patch whereas bacterioopsin do not.<BR>Recently, the amino acid sequence of bacteriorhodopsin has been determined.<BR>The retinal is bound as a protonated Schiff base to the ∈-amino group of a lysine residue.
日本生物物理学会の論文