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Kringle 2 mediates high affinity binding of plasminogen to an internal sequence in streptococcal surface protein PAM.

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Author

  • AC Wistedt
  • Heike Kotarsky
  • D Marti
  • Ulrika Ringdahl
  • FJ Castellino
  • J Schaller
  • Ulf Sjöbring

Summary, in English

Many cells express receptors for plasminogen (Pg), although the responsible molecules in most cases are poorly defined. In contrast, the group A streptococcal surface protein PAM contains a domain with two 13-amino acid residue long repeated sequences (a1 and a2) responsible for Pg binding. Here we identify the region in Pg that interacts with PAM. A radiolabeled proteolytic plasminogen fragment containing the first three kringles (K1-K3) interacted with streptococci expressing PAM or a chimeric surface protein harboring the a1a2 sequence. In contrast, plasminogen fragments containing kringle 4 or kringle 5 and the activable serine proteinase domain failed to bind to PAM-expressing group A streptococci. A synthetic and a recombinant polypeptide containing the a1a2 sequence both bound to immobilized recombinant K2 (rK2) but not to rK1 or rK3. The interaction between the a repeat region and rK2 was reversible, and rK2 completely blocked the binding of Pg to the a1a2 region. The binding of the a repeat containing polypeptide to K2 occurred with an equilibrium association constant of 4.5 x 10(7) M-1, as determined by surface plasmon resonance, a value close to that (1.6 x 10(7) M-1) calculated for the a1a2-Pg interaction. Inhibition experiments suggested involvement of the lysine-binding site of K2 in the interaction. These data demonstrate that K2 contains the major Pg-binding site for PAM, providing the first well defined example of an interaction between an internal Pg-binding region in a protein and a single kringle domain.

Publishing year

1998

Language

English

Pages

24420-24424

Publication/Series

Journal of Biological Chemistry

Volume

273

Issue

38

Document type

Journal article

Publisher

American Society for Biochemistry and Molecular Biology

Topic

  • Clinical Medicine

Status

Published

ISBN/ISSN/Other

  • ISSN: 1083-351X