TY - JOUR
T1 - The Mechanism of a Bacterial Plasminogen Activator Intermediate between Streptokinase and Staphylokinase
AU - Sazonova, Irina Y.
AU - Houng, Aiilyan K.
AU - Chowdhry, Shakeel A.
AU - Robinson, Brian R.
AU - Hedstrom, Lizbeth
AU - Reed, Guy L.
PY - 2001/4/20
Y1 - 2001/4/20
N2 - The therapeutic properties of plasminogen activators are dictated by their mechanism of action. Unlike staphylokinase, a single domain protein, streptokinase, a 3-domain (α, β, and γ) molecule, nonproteolytically activates human (h)-plasminogen and protects plasmin from inactivation by α2-antiplasmin. Because a streptokinase-like mechanism was hypothesized to require the streptokinase γ-domain, we examined the mechanism of action of a novel two-domain (α,β) Streptococcus uberis plasminogen activator (SUPA). Under conditions that quench trace plasmin, SUPA nonproteolytically generated an active site in bovine (b)-plasminogen. SUPA also competitively inhibited the inactivation of plasmin by α2-antiplasmin. Still, the lag phase in active site generation and plasminogen activation by SUPA was at least 5-fold longer than that of streptokinase. Recombinant streptokinase γ-domain bound to the b-plasminogen·SUPA complex and significantly reduced these lag phases. The SUPA-b·plasmin complex activated b-plasminogen with kinetic parameters comparable to those of streptokinase for h-plasminogen. The SUPA-b·plasmin complex also activated h-plasminogen but with a lower kcat (25-fold) and kcat/Km (7.9-fold) than SK. We conclude that a γ-domain is not required for a streptokinase-like activation of b-plasminogen. However, the streptokinase γ-domain enhances the rates of active site formation in b-plasminogen and this enhancing effect may be required for efficient activation of plasminogen from other species.
AB - The therapeutic properties of plasminogen activators are dictated by their mechanism of action. Unlike staphylokinase, a single domain protein, streptokinase, a 3-domain (α, β, and γ) molecule, nonproteolytically activates human (h)-plasminogen and protects plasmin from inactivation by α2-antiplasmin. Because a streptokinase-like mechanism was hypothesized to require the streptokinase γ-domain, we examined the mechanism of action of a novel two-domain (α,β) Streptococcus uberis plasminogen activator (SUPA). Under conditions that quench trace plasmin, SUPA nonproteolytically generated an active site in bovine (b)-plasminogen. SUPA also competitively inhibited the inactivation of plasmin by α2-antiplasmin. Still, the lag phase in active site generation and plasminogen activation by SUPA was at least 5-fold longer than that of streptokinase. Recombinant streptokinase γ-domain bound to the b-plasminogen·SUPA complex and significantly reduced these lag phases. The SUPA-b·plasmin complex activated b-plasminogen with kinetic parameters comparable to those of streptokinase for h-plasminogen. The SUPA-b·plasmin complex also activated h-plasminogen but with a lower kcat (25-fold) and kcat/Km (7.9-fold) than SK. We conclude that a γ-domain is not required for a streptokinase-like activation of b-plasminogen. However, the streptokinase γ-domain enhances the rates of active site formation in b-plasminogen and this enhancing effect may be required for efficient activation of plasminogen from other species.
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U2 - 10.1074/jbc.M009265200
DO - 10.1074/jbc.M009265200
M3 - Article
C2 - 11278483
AN - SCOPUS:0035918292
SN - 0021-9258
VL - 276
SP - 12609
EP - 12613
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 16
ER -