Crystallization and preliminary diffraction analysis of Wzi, a member of the capsule export and assembly pathway in Escherichia coli

Abstract

External polysaccharide capsules provide a physical barrier that is employed by many species of bacteria for the purposes of host evasion and persistence. Wzi is a 53 kDa outer membrane beta-barrel protein that is thought to play a role in the attachment of group 1 capsular polysaccharides to the cell surface. The purification and crystallization of an Escherichia coli homologue of Wzi is reported and diffraction data from native and selenomethionine-incorporated protein crystals are presented. Crystals of C-terminally His(6)-tagged Wzi diffracted to 2.8 A resolution. Data processing showed that the crystals belonged to the orthorhombic space group C222, with unit-cell parameters a = 128.8, b = 152.8, c = 94.4 A, alpha = beta = gamma = 90 degrees. A His-tagged selenomethionine-containing variant of Wzi has also been crystallized in the same space group and diffraction data have been recorded to 3.8 A resolution. Data processing shows that the variant crystal has similar unit-cell parameters to the native crystal.