PMID:15090537
| Citation |
Beis, K, Collins, RF, Ford, RC, Kamis, AB, Whitfield, C and Naismith, JH (2004) Three-dimensional structure of Wza, the protein required for translocation of group 1 capsular polysaccharide across the outer membrane of Escherichia coli. J. Biol. Chem. 279:28227-32 |
|---|---|
| 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-A 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-A 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 A, whereas the smaller is almost circular with a diameter of 90 A. In the center of the complex and enclosed by the four symmetrical arms is a small elliptical cagelike cavity of approximately 40 A 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. |
| Links |
PubMed Online version:10.1074/jbc.M402913200 |
| Keywords |
Bacterial Outer Membrane Proteins/chemistry; Biological Transport; Cryoelectron Microscopy; Crystallization; Crystallography, X-Ray; Dimerization; Escherichia coli Proteins/chemistry; Image Processing, Computer-Assisted; Microscopy, Electron; Models, Molecular; Polysaccharides/chemistry; Protein Conformation; Protein Structure, Tertiary; Protein Transport |
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