title: A tool for the qualitative comparison of membrane-embedded and detergent-solubilized membrane protein structures in projection.
abstract: The calculation of projection structures (PSs) from Protein Data Bank (PDB)-coordinate files of membrane proteins is not well-established. Reports on such attempts exist but are rare. In addition, the different procedures are barely described and thus difficult if not impossible to reproduce. Here we present a simple, fast and well-documented method for the calculation and visualization of PSs from PDB-coordinate files of membrane proteins: the projection structure visualization (PSV)-method. The PSV-method was successfully validated using the PS of aquaporin-1 (AQP1) from 2D crystals and cryo-transmission electron microscopy, and the PDB-coordinate file of AQP1 determined from 3D crystals and X-ray crystallography. Besides AQP1, which is a relatively rigid protein, we also studied a flexible membrane transport protein, i.e. the L-arginine/agmatine antiporter AdiC. Comparison of PSs calculated from the existing PDB-coordinate files of substrate-free and L-arginine-bound AdiC indicated that conformational changes are detected in projection. Importantly, structural differences were found between the PSV-method calculated PSs of the detergent-solubilized AdiC proteins and the PS from cryo-TEM of membrane-embedded AdiC. These differences are particularly exciting since they may reflect a different conformation of AdiC induced by the lateral pressure in the lipid bilayer.
authors.affiliation: Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland.
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Jeckelmann
authors.forename: Manuel
authors.initials: M
authors.lastname: Palacin
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Fotiadis
mesh_terms: D000818:Animals; D018360:Crystallography, X-Ray / Q000379:methods; D006801:Humans; D008565:Membrane Proteins / Q000737:chemistry* / Q000648:ultrastructure*; D046529:Microscopy, Electron, Transmission / Q000379:methods
chemical_list: D008565:Membrane Proteins