Three-dimensional structure of Wza, the protein required for translocation of group 1 capsular polysaccharide across the outer membrane of Echerichia coli

K Beis, RF Collins, RC Ford, AB Kamis, C Whitfield, James Henderson Naismith

Research output: Contribution to journalArticlepeer-review

49 Citations (Scopus)

Abstract

Wza is a highly conserved multimeric outer membrane protein complex required for the surface expression of the serotype K30 group 1 capsular polysaccharide in Escherichia coli. Here we present the first three-dimensional structure of this type of polysaccharide exporter at a 15.5-Angstrom resolution obtained using single particle averaging on a dataset of cryo-negatively stained protein. Previous structural studies on purified Wza have revealed a homo-oligomeric ring structure that is most probably composed of eight subunits. Symmetry analysis of the three-dimensional structure combined with biochemical two-and three-dimensional crystallographic data strongly suggest that Wza is an octameric complex with a C4 quasi-rotational symmetry and is organized as a tetramer of dimeric subunits. Wza is best described as a stack of two 4-Angstrom high rings with differing diameters providing a mushroom-like aspect from the side. The larger ring has a distinctive square shape with a diameter of 115 Angstrom, whereas the smaller is almost circular with a diameter of 90 Angstrom. In the center of the complex and enclosed by the four symmetrical arms is a small elliptical cagelike cavity of similar to 40 Angstrom in diameter. The central cavity is effectively sealed at the top and bottom of the complex but has small inter-arm holes when viewed from the side. We discuss the structure of this complex and implications in the surface translocation of cell-surface polysaccharide.

Original languageEnglish
Pages (from-to)28227-28232
Number of pages6
JournalJournal of Biological Chemistry
Volume279
DOIs
Publication statusPublished - 2 Jul 2004

Keywords

  • BACTERIAL CHANNEL-TUNNELS
  • TWO-DIMENSIONAL CRYSTALS
  • GRAM-NEGATIVE BACTERIA
  • ELECTRON-MICROSCOPY
  • PSEUDOMONAS-AERUGINOSA
  • TYROSINE AUTOKINASE
  • MULTIDRUG EFFLUX
  • SECRETIN PULD
  • EXPORT
  • EXPRESSION

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