title: The directed cooperative assembly of proteorhodopsin into 2D and 3D polarized arrays.
abstract: Proteorhodopsin is the membrane protein used by marine bacterioplankton as a light-driven proton pump. Here, we describe a rapid cooperative assembly process directed by universal electrostatic interactions that spontaneously organizes proteorhodopsin molecules into ordered arrays with well defined orientation and packing density. We demonstrate the charge density-matching mechanism that selectively controls the assembly process. The interactions among different components in the system are tuned by varying their charge densities to yield different organized transmembrane protein arrays: (i) a bacteriorhodopsin purple membrane-like structure where proteorhodopsin molecules are cooperatively arranged with charged lipids into a 2D hexagonal lattice; (ii) selected liquid-crystalline states in which crystalline lamellae made up of the coassembled proteorhodopsin and charged lipid molecules are coupled three-dimensionally with polarized proteorhodopsin orientation persisting through the macroscopic scale. Understanding this rapid electrostatically driven assembly process sheds light on organizing membrane proteins in general, which is a prerequisite for membrane protein structural and mechanistic studies as well as in vitro applications.
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA 93106, USA.
authors.forename: Hongjun
authors.initials: H
authors.lastname: Liang
authors.forename: Gregg
authors.initials: G
authors.lastname: Whited
authors.forename: Chi
authors.initials: C
authors.lastname: Nguyen
authors.forename: Galen D
authors.initials: GD
authors.lastname: Stucky
mesh_terms: D008055:Lipids / Q000737:chemistry; D020836:Protein Structure, Quaternary; D018717:Purple Membrane / Q000737:chemistry; D012243:Rhodopsin / Q000737:chemistry* / Q000648:ultrastructure; D025604:Rhodopsins, Microbial; D012995:Solubility; D014961:X-Ray Diffraction
chemical_list: D008055:Lipids; D025604:Rhodopsins, Microbial; C413548:proteorhodopsin; D012243:Rhodopsin