Studies on .ALPHA.2-plasmin inhibitor fragment T-11. III. Structure - activity relationships among the fragments of T-11, the plasminogen binding site(s) of human .ALPHA.2-plasmin inhibitor.

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Abstract
Twelve shortened fragments of peptide T-11, which is a part of human .alpha.2-plasmin inhibitor and contains its plasmin(ogen)-binding site(s) were synthesized by a conventional solution method. The dissociation constants for the interaction between these synthetic fragments and plasmin were determined. Among these fragments, the octadecapeptide containing C-terminal lysine of T-11, which consists of 26 amino acids, was found to be the smallest active fragment of T-11. The N-terminal and the central portion fragments of T-11 possessed no binding activity. The heptadecapeptide which has the same sequence as the octadecapeptide but lacks the C-terminal lysine showed no binding activity. The hexadecapeptide containing the C-terminal lysine but lacking the 10th lysine in T-11 scarcely exhibited the activity. Thus, the lysine resides at positions 10 and 26 in T-11 must be important for the activity.