title: Lipid bilayer composition can influence the orientation of proteorhodopsin in artificial membranes.
abstract: Artificial membrane systems allow researchers to study the structure and function of membrane proteins in a matrix that approximates their natural environment and to integrate these proteins in ex vivo devices such as electronic biosensors, thin-film protein arrays, or biofuel cells. Given that most membrane proteins have vectorial functions, both functional studies and applications require effective control over protein orientation within a lipid bilayer. In this work, we explored the role of the bilayer surface charge in determining transmembrane protein orientation and functionality during formation of proteoliposomes. We reconstituted a model vectorial ion pump, proteorhodopsin, in liposomes of opposite charges and varying charge densities and determined the resultant protein orientation. Antibody-binding assay and proteolysis of proteoliposomes showed physical evidence of preferential orientation, and functional assays verified the vectorial nature of ion transport in this system. Our results indicate that the manipulation of lipid composition can indeed control orientation of an asymmetrically charged membrane protein, proteorhodopsin, in liposomes.
authors.affiliation: Department of Chemical Engineering and Materials Science, University of California, Davis, Davis, California; Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California; Physics and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California.
authors.forename: Ramya
authors.initials: R
authors.lastname: Tunuguntla
authors.forename: Mangesh
authors.initials: M
authors.lastname: Bangar
authors.forename: Kyunghoon
authors.initials: K
authors.lastname: Kim
authors.forename: Pieter
authors.initials: P
authors.lastname: Stroeve
authors.forename: Caroline M
authors.initials: CM
authors.lastname: Ajo-Franklin
authors.forename: Aleksandr
authors.initials: A
authors.lastname: Noy
mesh_terms: D001692:Biological Transport; D008027:Light; D008051:Lipid Bilayers / Q000737:chemistry* / Q000378:metabolism*; D008567:Membranes, Artificial; D011510:Proteolipids / Q000378:metabolism; D059748:Proteolysis; D017494:Proton Pumps / Q000378:metabolism; D011522:Protons; D012243:Rhodopsin / Q000737:chemistry / Q000378:metabolism*; D025604:Rhodopsins, Microbial; D013499:Surface Properties
chemical_list: D008051:Lipid Bilayers; D008567:Membranes, Artificial; D011510:Proteolipids; D017494:Proton Pumps; D011522:Protons; D025604:Rhodopsins, Microbial; C020485:proteoliposomes; C413548:proteorhodopsin; D012243:Rhodopsin
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