title: The structure of OmpF porin in a tetragonal crystal form.
abstract: OmpF porin is a trimeric integral membrane protein responsible for the passive transport of small hydrophilic molecules, such as nutrients and waste products, across the outer membrane of Escherichia coli. Very few membrane proteins have been crystallized in three dimensions, yet this stable protein can be obtained in several crystal forms. Comparison of the structures of the same membrane protein in two different packing environments is of major interest, because it allows us to explore the integrity of the structure outside the natural membrane environment.
  
  
  
  The structure of OmpF porin in a tetragonal crystal form with two trimers per asymmetric unit has been determined at 3.2 A resolution and compared with that obtained previously in a trigonal crystal form. The lattice contacts involve only polar atoms, whereas extensive hydrophobic protein-protein interactions were found in the trigonal lattice. The trimer structure is virtually identical in both.
  
  
  
  Our comparison reveals that the overall structure of OmpF is not influenced by crystal lattice constraints and, thus, presumably bears close resemblance to the in vivo structure. The tetragonal crystal structure has provided the starting model for the phasing of neutron diffraction data obtained from this crystal form, as described in an accompanying article.
authors.affiliation: Department of Structural Biology, University of Basel, Switzerland.
authors.forename: S W
authors.initials: SW
authors.lastname: Cowan
authors.affiliation: Department of Microbiology, University of Basel, Switzerland.
authors.forename: R M
authors.initials: RM
authors.lastname: Garavito
authors.affiliation: Department of Structural Biology, University of Basel, Switzerland.
authors.forename: J N
authors.initials: JN
authors.lastname: Jansonius
authors.affiliation: Department of Structural Biology, University of Basel, Switzerland.
authors.forename: J A
authors.initials: JA
authors.lastname: Jenkins
authors.affiliation: Department of Structural Biology, University of Basel, Switzerland.
authors.forename: R
authors.initials: R
authors.lastname: Karlsson
authors.affiliation: Department of Microbiology, University of Basel, Switzerland.
authors.forename: N
authors.initials: N
authors.lastname: König
authors.affiliation: European Molecular Biology Laboratory, Heidelberg, Germany.
authors.forename: E F
authors.initials: EF
authors.lastname: Pai
authors.affiliation: Department of Structural Biology, University of Basel, Switzerland.
authors.forename: R A
authors.initials: RA
authors.lastname: Pauptit
authors.affiliation: Daresbury Laboratory, Cheshire, UK.
authors.forename: P J
authors.initials: PJ
authors.lastname: Rizkallah
authors.affiliation: Department of Microbiology, University of Basel, Switzerland.
authors.forename: J P
authors.initials: JP
authors.lastname: Rosenbusch
authors.affiliation: Department of Microbiology, University of Basel, Switzerland.
authors.forename: G
authors.initials: G
authors.lastname: Rummel
authors.affiliation: Department of Structural Biology, University of Basel, Switzerland.
authors.forename: T
authors.initials: T
authors.lastname: Schirmer
mesh_terms: D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry*; D018360:Crystallography, X-Ray / Q000379:methods; D007495:Iridium / Q000737:chemistry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010984:Platinum / Q000737:chemistry; D011487:Protein Conformation; D017510:Protein Folding; D012984:Software; D013696:Temperature
chemical_list: D001425:Bacterial Outer Membrane Proteins; D007495:Iridium; D010984:Platinum