Haemophilus ducreyi Mediator of Fibrinogen Binding in Trimeric Autotransporter DsrA Is a Major

infection (9).DsrAbelongstothefamilyoftrimericautotransporteradhesin(TAA),multifunctionaloutermembraneproteinsinvolvedinad-hesionandserumresistance(10).Structurally,TAAproteinscon-tainthreedomains:anN-terminalsignalpeptide,apassengerdo-main, and a C-terminal translocator region (11). The highlyconservedtranslocatordomainofTAA,whichservesasthecrite-rion for inclusion of proteins in this family, anchors TAA in theoutermembrane.ThepassengerdomainofTAAisinvolvedinitsdifferent functions. As the name implies, TAA proteins are ex-pressed as trimers at the surface of bacterial cells, and trimeriza-tion of the passenger domain is required for structural stability,adhesiveactivity,andvirulence(12,13).Theprototypicalproteinfor this group of proteins, YadA from