Structure of DraD invasin from uropathogenic Escherichia coli: a dimer with swapped β-tails

The dra gene cluster of uropathogenic strains of Escherichia coli produces proteins involved in bacterial attachment to and invasion of the eukaryotic host tissues. The crystal structure of a construct of E. coli DraD possessing an additional C-­terminal extension of 13 amino acids, including a His₆ tag, has been solved at a resolution of 1.05 Å. The protein forms symmetric dimers through the exchange of the C-terminal β-­strands, which participate in the immunoglobulin-like β-­sandwich fold of each subunit. This structure confirms that DraD is able to act as an acceptor in the donor-strand complementation mechanism of fiber formation but, in contrast to DraE adhesin, its native sequence does not have a donor strand; therefore, DraD can only be located at the tip of the fiber.