Thrombospondin interaction with plasminogen. Evidence for binding to a
specific region of the kringle structure of plasminogen
P DePoli, T Bacon-Baguley, S Kendra-Franczak, MT Cederholm and DA Walz
Department of Physiology, Wayne State University, Detroit, MI 48201.
Platelet thrombospondin interacts with plasminogen in a specific and
saturable manner. Thrombospondin was found to specifically bind to
plasminogen and the nonenzyme chain of plasmin. Preincubation of 125I-
labeled thrombospondin with 30 mmol/L lysine was without effect in the
binding of thrombospondin to immobilized plasminogen; preincubation of
125I-labeled plasminogen with 30 mmol/L lysine, on the other hand,
significantly reduced the binding of plasminogen to immobilized
thrombospondin, suggesting that the interaction of thrombospondin with
plasminogen is not the direct result of the lysine binding sites of
plasminogen. Arginine and benzamidine, ligands known to specifically bind
to the kringle 5 domain of plasminogen, blocked the binding of
thrombospondin to plasminogen. Limited elastase proteolysis of plasminogen
and plasmin resulted in the generation of two distinct thrombospondin
binding domains, one of which was retained on lysine- agarose. The
isolation and amino-terminal analysis of these domains following elastase
proteolysis of plasminogen identified them, respectively, as a domain
containing kringle structures 4 and 5 and plasmin and the other domain
consisting of kringle 5-plasmin. A 16- residue synthetic peptide, which
represents the amino acids linking kringle 4 to kringle 5 (residues 435-450
of native plasminogen), was without effect in either binding to
thrombospondin or blocking the binding of thrombospondin to plasminogen.
Plasminogen, therefore, possesses a single thrombospondin interactive site
that is independent of, but influenced by, the lysine binding site
containing kringle structures and most likely is located within the kringle
5 domain.
Volume 73,
Issue 4,
pp. 976-982,
03/01/1989
Copyright © 1989 by The American Society of Hematology
