title: A common channel-forming motif in evolutionarily distant porins.
abstract: Four new crystal packings of Escherichia coli porins are presented (phosphoporin, maltoporin, and two crystal forms of matrix porin). These were determined by molecular replacement methods using a polyalanine trial model acquired from the refined coordinates of porin from Rhodobacter capsulatus. The successful molecular replacement shows that the dominant motif found in R. capsulatus porin (a 16-stranded antiparallel beta-barrel) also applies to the E. coli porins, despite the lack of significant amino acid sequence homology. A 30 degrees-40 degrees tilt of the beta-strands with respect to the membrane normal was derived from the intensity distributions in the X-ray diffraction patterns for each porin studied, stressing their similarity. In view of the evolutionary distance between enteric and photosynthetic bacteria, the antiparallel beta-barrel may have significance as a basic structural motif for the formation of bacterial membrane channel structures.
authors.affiliation: Biocenter, University of Basel, Switzerland.
authors.forename: R A
authors.initials: RA
authors.lastname: Pauptit
authors.forename: T
authors.initials: T
authors.lastname: Schirmer
authors.forename: J N
authors.initials: JN
authors.lastname: Jansonius
authors.forename: J P
authors.initials: JP
authors.lastname: Rosenbusch
authors.forename: M W
authors.initials: MW
authors.lastname: Parker
authors.forename: A D
authors.initials: AD
authors.lastname: Tucker
authors.forename: D
authors.initials: D
authors.lastname: Tsernoglou
authors.forename: M S
authors.initials: MS
authors.lastname: Weiss
authors.forename: G E
authors.initials: GE
authors.lastname: Schultz
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry*; D005075:Biological Evolution; D003198:Computer Simulation; D003460:Crystallization; D004926:Escherichia coli / Q000737:chemistry; D007473:Ion Channels / Q000737:chemistry*; D008958:Models, Molecular; D018272:Porins; D016354:Rhodobacter capsulatus / Q000737:chemistry; D014961:X-Ray Diffraction
chemical_list: D001425:Bacterial Outer Membrane Proteins; D007473:Ion Channels; D018272:Porins