PLASMINOGEN KRINGLE-4 BINDS THE HEPTAPEPTIDE FRAGMENT-44-50 OF THE PLASMINOGEN N-TERMINAL PEPTIDE

The interaction between the plasminogen kringle 4 module and a synthet ic peptide corresponding to the tryptic heptapeptide fragment Ala-Phe- Gln-Tyr-His-Ser-Lys (AFQYHSK), segment 44-50 of the plasminogen N-term inal peptide (Wiman and Wallen, Eur J Biochem 1975; 50: 489-494), has been investigated by H-1-NMR spectroscopy. AFQYHSK, as well as the sho rter fragments thereof, FQYHSK, QYHSK and YHSK, all bound to kringle 4 with equilibrium association constant (K-a) values ranging between 2. 5 and 8.5 mM(-1). The NMR evidence also indicates that binding is medi ated by the canonical kringle lysine binding site and involves the C-t erminal Lys residue of the ligand peptide. The results (a) support a p otential interaction between plasminogen Lys-binding kringles and the N-terminal activation peptide, and (b) unambiguously demonstrate the c apability of such kringles to bind polypeptides ending with C-terminal lysine.