IMMUNOHISTOLOGICAL LOCALIZATION OF THE MRKD ADHESIN IN THE TYPE-3 FIMBRIAE OF KLEBSIELLA-PNEUMONIAE

The adhesive minor protein MrkD of the type 3 fimbria of Klebsiella pn eumoniae was expressed and purified from Escherichia coil as a fusion protein with an N-terminal polyhistidine tail. Polyclonal antibodies r aised against MrkD specifically recognized the MrkD peptide in Western blots of fimbrial preparations. Immunoelectron microscopic analyses s howed that the anti-MrkD immunoglobulins bound to the tip of the plasm id-encoded variant of the type 3 fimbria of K. pneumoniae, whereas no binding to the chromosomally encoded MrkD-deficient type 3 fimbrial va riant of K. pneumoniae was detected. Immunoglobulins from an antiserum raised against purified type 3 fimbrial filaments bound laterally to both type 3 fimbrial variants. The anti-MrkD antibodies also bound to the tip of a papG deletion derivative of the E. coli P fimbria complem ented with mrkD, indicating that MrkD structurally complements a PapG mutation in the P fimbria of E. coli.