Role of the streptokinase alpha-domain in the interactions of streptokinase with plasminogen and plasmin.

Bean RR, Verhamme IM, Bock PE
J Biol Chem. 2005 280 (9): 7504-10

PMID: 15623524 · PMCID: PMC2292463 · DOI:10.1074/jbc.M411637200

The role of the streptokinase (SK) alpha-domain in plasminogen (Pg) and plasmin (Pm) interactions was investigated in quantitative binding studies employing active site fluorescein-labeled [Glu]Pg, [Lys]Pg, and [Lys]Pm, and the SK truncation mutants, SK-(55-414), SK-(70-414), and SK-(152-414). Lysine binding site (LBS)-dependent and -independent binding were resolved from the effects of the lysine analog, 6-aminohexanoic acid. The mutants bound indistinguishably, consistent with unfolding of the alpha-domain on deletion of SK-(1-54). The affinity of SK for [Glu]Pg was LBS-independent, and although [Lys]Pg affinity was enhanced 13-fold by LBS interactions, the LBS-independent free energy contributions were indistinguishable. alpha-Domain truncation reduced the affinity of SK for [Glu]Pg 2-7-fold and [Lys]Pg

MeSH Terms (20)

Aminocaproic Acid Binding Sites Catalysis Catalytic Domain Chlorine Fibrinolysin Gene Deletion Humans Lipopolysaccharides Lysine Microscopy, Fluorescence Mutation Plasminogen Protein Binding Protein Conformation Protein Folding Protein Structure, Tertiary Recombinant Proteins Streptokinase Thermodynamics

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