Decorin-
binding protein A (
DbpA) of Borrelia burgdorferi mediates bacterial adhesion to
heparin and
dermatan sulfate associated with
decorin. Lysines K82, K163, and K170 of
DbpA are known to be important for in vitro interaction with
decorin, and the
DbpA structure, initially solved by nuclear magnetic resonance (NMR) spectroscopy, suggests these
lysine residues colocalize in a pocket near the C terminus of the
protein. In the current study, we solved the structure of
DbpA from B. burgdorferi strain 297 using X-ray crystallography and confirmed the existing NMR structural data. In vitro binding experiments confirmed that recombinant
DbpA proteins with mutations in K82, K163, or K170 did not bind
decorin, which was due to an inability to interact with
dermatan sulfate. Most importantly, we determined that the in vitro binding defect observed upon mutation of K82, K163, or K170 in
DbpA also led to a defect during
infection. The infectivity of B. burgdorferi expressing individual
dbpA lysine point mutants was assessed in mice challenged via needle inoculation. Murine
infection studies showed that strains expressing
dbpA with mutations in K82, K163, and K170 were significantly attenuated and could not be cultured from any tissue. Proper expression and cellular localization of the mutated
DbpA proteins were examined, and NMR spectroscopy determined that the mutant
DbpA proteins were structurally similar to wild-type
DbpA. Taken together, these data showed that lysines K82, K163, and K170 potentiate the binding of
DbpA to
dermatan sulfate and that an interaction(s) mediated by these lysines is essential for B. burgdorferi murine
infection.