Outer membrane polysaccharide transporter
The extracellular polysaccharide colanic acid is produced by species of the family Enterobacteriaceae. In Escherichia coli strain K12 the colanic acid cluster comprises 19 genes. The wzx gene encodes a protein with multiple transmembrane segments that may function in export of the colanic acid repeat unit from the cytoplasm into the periplasm in a process analogous to O-unit export. The colanic acid gene clusters may be involved in the export of polysaccharide from the cell. References

Outer membrane proteins
Protein families