A surface-exposed DraD protein of uropathogenic Escherichia coli bearing Dr fimbriae may be expressed and secreted independently from DraC usher and DraE adhesin.

The dra gene cluster, expressed by uropathogenic Escherichia coli strains, determines bacterial attachment and invasion. The Dr fimbrial structures formed at the bacterial cell surface are composed of DraE subunits. The Dr fimbriae-coding cluster contains six open reading frames--draA, draB, draC, draD, draP and draE--among which the draE gene encodes the structural fimbrial subunit DraE. Very little is known about E. coli surface expression of the draD gene product. The expression of DraD and its role in the biogenesis of Dr fimbriae were determined by constructing mutants in the dra operon and by immunoblot and immunofluorescence experiments. In this study, DraD was found to be a surface-exposed protein. The expression of DraD was independent of the DraC usher and DraE fimbrial subunits. Polymerization of DraE fimbrial subunits into fimbrial structures did not require expression of the DraD protein.