title: Binding of human plasminogen to Borrelia burgdorferi.
abstract: We studied the binding of plasminogen to Borrelia burgdorferi, a spirochete which causes Lyme disease and produces no endogenous proteases which digest extracellular matrix proteins. Using 125I-labeled plasminogen, we demonstrated that B. burgdorferi bound human plasminogen and that this binding was inhibitable with unlabeled plasminogen. 125I-labeled plasminogen binding by B. burgdorferi was also inhibited by the lysine analog epsilon-aminocaproic acid. There was no significant difference in the binding of Glu- or Lys-plasminogen to B. burgdorferi. Binding of plasminogen was similar in low-passage (infectious) and high-passage (noninfectious) isolates of B. burgdorferi. Plasminogen bound to the surface of B. burgdorferi could be converted into plasmin by a human urokinase-type plasminogen activator. 125I-labeled plasminogen ligand blots of borrelial membrane proteins demonstrated two prominent binding proteins at approximately 70 and approximately 30 kDa. By Western blot (immunoblot), the 30-kDa protein was found to be outer surface protein A (Osp A) of B. burgdorferi. 125I-labeled plasminogen binding to both the 70-kDa protein and Osp A was inhibited by approximately 90% with a 1,000-fold excess of unlabeled plasminogen. By scanning densitometry, the 70-kDa band bound > 10 time more 125I-labeled plasminogen than did Osp A. An Osp A-deficient mutant of B. burgdorferi and wild-type B. burgdorferi bound equal amounts of 125I-labeled plasminogen. Ligand blots of membrane proteins from an Osp A-deficient mutant showed association of 125I-labeled plasminogen at only the 70-kDa protein. Two-dimensional gel electrophoresis showed that the 70-kDa protein had a pI of approximately 5.3, clearly separable from Osp A. The association of host plasmin(ogen) with borrelial surface proteins provides a mechanism by which B. burgdorferi can digest extracellular matrix and disseminate.
authors.affiliation: Division of Geographic Medicine and Infectious Diseases, Tufts University School of Medicine, New England Medical Center, Boston, Massachusetts 02111, USA.
authors.forename: L T
authors.initials: LT
authors.lastname: Hu
authors.forename: G
authors.initials: G
authors.lastname: Perides
authors.forename: R
authors.initials: R
authors.lastname: Noring
authors.forename: M S
authors.initials: MS
authors.lastname: Klempner
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism; D015748:Borrelia burgdorferi Group / Q000502:physiology*; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism; D010958:Plasminogen / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D008565:Membrane Proteins; D010958:Plasminogen