Control of the integral membrane proton pump, bacteriorhodopsin, by purple membrane lipids of Halobacterium halobium.
Brief exposure of purple membrane (PM) to dilute Triton X-100 eliminates the actinic light effect on the relative amounts of fast M (Mf) and slow M (Ms) intermediates and alters the character and kinetics of the photocycle, without destroying the native BR trimers (Mukhopadhyay et al., 1994). Particular membrane lipids are removed during the Triton treatment, and adding back an extract of membrane lipids can repair most of the affected photocycle behavior (Dracheva et al., 1996). This paper defines conditions which are important in the reconstitution procedure, using a group of quantitative parameters which measure the extents of damage and repair. Circular dichroism in both the UV and visible ranges shows that Triton can disturb both the secondary structure of BR and its ability to polymerize into trimers. Whereas the damage to protein conformation could be reversed by lipids alone, the formation of trimers and recovery of normal photocycle behavior required both lipids and a high salt concentration.
Mukhopadhyay
A K
AK
Laboratory of Cell Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
Dracheva
S
S
Bose
S
S
Hendler
R W
RW
D001436:Bacteriorhodopsins / Q000737:chemistry / Q000378:metabolism*; D002942:Circular Dichroism; D003902:Detergents / Q000494:pharmacology; D019617:Halobacterium salinarum / Q000737:chemistry / Q000378:metabolism*; D008027:Light; D008563:Membrane Lipids / Q000378:metabolism* / Q000494:pharmacology; D017830:Octoxynol / Q000494:pharmacology; D017494:Proton Pumps / Q000378:metabolism*; D018717:Purple Membrane / Q000737:chemistry / Q000378:metabolism*; D012965:Sodium Chloride / Q000494:pharmacology
D003902:Detergents; D008563:Membrane Lipids; D017494:Proton Pumps; D012965:Sodium Chloride; D001436:Bacteriorhodopsins; D017830:Octoxynol