title: Projection maps of three members of the KdgM outer membrane protein family.
abstract: We present the projection structures of the three outer membrane porins KdgM and KdgN from Erwinia chrysanthemi and NanC from Escherichia coli, based on 2D electron crystallography. A wide screening of 2D crystallization conditions yielded tubular crystals of a suitable size and quality to perform high-resolution electron microscopy. Data processing of untilted samples allowed us to separate the information of the two crystalline layers and resulted in projection maps to a resolution of up to 7A. All three proteins exhibit a similar putative beta-barrel structure and the three crystal forms have the same symmetry. However, there are differences in the packing arrangements of the monomers as well as the densities of the projections. To interpret these projections, secondary structure prediction was performed using beta-barrel specific prediction algorithms. The predicted transmembrane beta-barrels have a high similarity in the arrangement of the putative beta-strands and the loops, but do not match those of OmpG, a related protein porin whose structure was solved.
authors.affiliation: Maurice E. Müller Institute for Structural Biology, Biozentrum, University of Basel, Klingelbergstrasse 50/70, CH-4056 Basel, Switzerland.
authors.forename: Gian A
authors.initials: GA
authors.lastname: Signorell
authors.forename: Mohamed
authors.initials: M
authors.lastname: Chami
authors.forename: Guy
authors.initials: G
authors.lastname: Condemine
authors.forename: Andreas D
authors.initials: AD
authors.lastname: Schenk
authors.forename: Ansgar
authors.initials: A
authors.lastname: Philippsen
authors.forename: Andreas
authors.initials: A
authors.lastname: Engel
authors.forename: Herve W
authors.initials: HW
authors.lastname: Remigy
mesh_terms: D000465:Algorithms; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry*; D003460:Crystallization / Q000379:methods; D016974:Dickeya chrysanthemi / Q000737:chemistry* / Q000648:ultrastructure; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000648:ultrastructure; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008055:Lipids; D046529:Microscopy, Electron, Transmission / Q000379:methods; D016624:Negative Staining / Q000379:methods; D018272:Porins / Q000737:chemistry* / Q000648:ultrastructure; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D011510:Proteolipids / Q000737:chemistry / Q000648:ultrastructure; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000648:ultrastructure; D013048:Specimen Handling / Q000379:methods
chemical_list: D001425:Bacterial Outer Membrane Proteins; D029968:Escherichia coli Proteins; D008055:Lipids; C528455:NanC protein, E coli; C109237:OmpF protein; C114347:OmpG protein, E coli; D018272:Porins; D011510:Proteolipids; D011993:Recombinant Fusion Proteins; C020485:proteoliposomes