Skizzle is a novel plasminogen- and plasmin-binding protein from Streptococcus agalactiae that targets proteins of human fibrinolysis to promote plasmin generation

Karen G. Wiles, Peter Panizzi, Heather K. Kroh, Paul E. Bock

Research output: Contribution to journalArticle

19 Scopus citations

Abstract

Skizzle (SkzL), secreted by Streptococcus agalactiae, has moderate sequence identity to streptokinase and staphylokinase, bacterial activators of human plasminogen (Pg). SkzL binds [Glu]Pg with low affinity (KD3-16 μM) and [Lys]Pg and plasmin (Pm) with indistinguishable high affinity (K D 80 and 50 nM, respectively). Binding of SkzL to Pg and Pmis completely lysine-binding site-dependent, as shown by the effect of the lysine analog, 6-aminohexanoic acid. Deletion of the COOH-terminal SkzL Lys 415 residue reduces affinity for [Lys]Pg and active site-blocked Pm 30-fold, implicating Lys415 in a lysine-binding site interaction with a Pg/Pm kringle. SkzL binding to active site fluorescein-labeled Pg/Pm analogs demonstrates distinct high and low affinity interactions. High affinity binding is mediated by Lys415, whereas the source of low affinity binding is unknown. SkzL enhances the activation of [Glu]Pg by urokinase (uPA) ∼20-fold, to a maximum rate indistinguishable from that for [Lys]Pg and [Glu]Pg activation in the presence of 6-aminohexanoic acid. SkzL binds preferentially to the partially extended β-conformation of [Glu]Pg, which is in unfavorable equilibrium with the compact α-conformation, thereby converting [Glu]Pg to the fully extended γ-conformation and accelerating the rate of its activation by uPA. SkzL enhances [Lys]Pg and [Glu]Pg activation by single-chain tissue-type Pg activator, ∼42- and ∼650-fold, respectively. SkzL increases the rate of plasma clot lysis by uPA and single-chain tissue-type Pg activator ∼2-fold, confirming its cofactor activity in a physiological model system. The results suggest a role for SkzL in S. agalactiae pathogenesis through fibrinolytic enhancement.

Original languageEnglish (US)
Pages (from-to)21153-21164
Number of pages12
JournalJournal of Biological Chemistry
Volume285
Issue number27
DOIs
StatePublished - Jul 2 2010
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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