OMA component of the group 1 K30 capsular polysaccharide, colanic acid, export system, Wza (Reid and Whitfield, 2005) (outer membrane porin constituent). The 3-d structure of the Wza/Wzc complex has been solved by Collins et al. (2007). It spans the periplasm, comprising a central constituent for complex formation. The x-ray structure shows an integral outer membrane transmembrane α-helical barrel with a large central cavity, similar to the secretin protein, PilQ (1.B.22.2.1) (Collins and Derrick, 2007).  Wza is an octameric α-helical outer membrane channel that directly exports nascent capsular polysaccharide chains through the Wza portal (Nickerson et al. 2014). Peptides based on the C-terminal D4 domain of Wza form transmembrane, ion conducting α-helical barrels. The helix barrel contains eight D4 peptides arranged in parallel (Mahendran et al. 2017).