Trapped translocation intermediates establish the route for export of capsular polysaccharides across Escherichia coli outer membranes
Nickerson NN., Mainprize IL., Hampton L., Jones ML., Naismith JH., Whitfield C.
Significance Exported long-chain polysaccharides protect the bacterial cell in harsh environments and play multifactorial roles in pathogenesis. These long-chain polysaccharides can take the form of secreted polymers (exopolysaccharides), or cell-associated capsular polysaccharides (CPSs) that form an organized surface layer called the capsule. Processes involved in the synthesis and export of CPSs are potential targets for new therapeutic strategies. Independent of their structures, these polymers rely on a family of outer membrane polysaccharide export (OPX) proteins for assembly on the cell surface. Combining structural information with site-specific in vivo photo–cross-linking provides direct evidence that the lumen of octameric complexes of Wza, a prototype OPX protein, is the export conduit for CPS.