title: Triton X-100 can alter the temporal sequence of the light-driven proton pump of archaerhodopsin 4.
abstract: We report that Triton X-100 can alter the temporal sequence of the light-induced proton uptake and release of archaerhodopsin 4 (AR4), a proton pumping protein in a species of Halobacteria from a Tibetan salt lake. Under physiological conditions, AR4 isolated from the bacterium exhibits a reversed temporal order of proton release and uptake compared to what is observed for bacteriorhodopsin (BR). However, in the presence of Triton X-100 early proton release was observed in AR4 at neutral pH by us. Further, this temporal order for light-driven proton release and uptake for AR4 was found to be recovered after the removal of Triton X-100 by Biobeads. This phenomenon of detergent-induced alteration of the order of proton release and uptake has not yet been reported in any other retinal-containing membrane protein such as BR. Our findings indicate that the function of AR4 is influenced by its self-assembled state, and meanwhile imply some subtle protein-lipid interactions or protein-protein interactions in adjusting the proton pumping behavior of AR4.
authors.affiliation: Key Laboratory of Molecular Engineering of Polymers of the Chinese Ministry of Education, Department of Macromolecular Science, Lab of Advanced Materials, Fudan University, Shanghai 200433, China.
authors.forename: Ming
authors.initials: M
authors.lastname: Ming
authors.forename: Yazhuo
authors.initials: Y
authors.lastname: Wang
authors.forename: Jia
authors.initials: J
authors.lastname: Wu
authors.forename: Dewang
authors.initials: D
authors.lastname: Ma
authors.forename: Qingguo
authors.initials: Q
authors.lastname: Li
authors.forename: Jiandong
authors.initials: J
authors.lastname: Ding
mesh_terms: D019843:Archaeal Proteins / Q000378:metabolism*; D001436:Bacteriorhodopsins / Q000378:metabolism; D002942:Circular Dichroism; D006863:Hydrogen-Ion Concentration; D008027:Light; D008863:Microspheres; D017830:Octoxynol / Q000494:pharmacology*; D017494:Proton Pumps / Q000378:metabolism*; D011522:Protons; D013997:Time Factors
chemical_list: D019843:Archaeal Proteins; D017494:Proton Pumps; D011522:Protons; D001436:Bacteriorhodopsins; D017830:Octoxynol