title: Structural comparison of native and deoxycholate-treated purple membrane.
abstract: Lipid-depleted purple membrane prepared by extraction with deoxycholate has been compared with the native structure. X-ray and electron diffraction photographs show a reduction in cell dimension from 62.4 to 57.3 A, and a substantial change in the distribution of diffraction intensity compared with the native specimens. Low-dose electron microscopy has been used to obtain a projected density map of lipid-depleted membranes. The projected structure shows that the deoxycholate treatment removes a boundary layer of lipid, which in the native form separates adjacent trimers of bacteriorhodopsin. The map also provides an improved estimate of the molecular envelope of the protein. A plausible arrangement for the lipid molecules in both the native and the lipid-depleted membranes is proposed, but the precise positions of individual molecules cannot yet be specified.
mesh_terms: D001436:Bacteriorhodopsins / Q000378:metabolism*; D002338:Carotenoids / Q000378:metabolism*; D003840:Deoxycholic Acid / Q000494:pharmacology*; D005583:Fourier Analysis; D006217:Halobacterium / Q000378:metabolism; D011487:Protein Conformation; D013329:Structure-Activity Relationship; D014961:X-Ray Diffraction
chemical_list: D003840:Deoxycholic Acid; D002338:Carotenoids; D001436:Bacteriorhodopsins