The β-domain of streptokinase affects several functionalities, including specific/proteolytic activity kinetics

Area of Science:

• Biochemistry and Molecular Biology
• Microbiology
• Thrombolytic Therapy

Background:

• Streptokinase (SK) is a crucial plasminogen activator used to dissolve blood clots.
• SK from Streptococcus groups A, C, and G comprises three domains: SKα, SKβ, and SKγ.
• Previous studies highlighted the SKβ domain's importance in activating human plasminogen.

Purpose of the Study:

• To investigate the role of the SKβ domain in various streptokinase functionalities.
• To analyze the impact of SKβ on activity kinetics, fibrinogen-bound plasminogen activation, and resistance to α2-antiplasmin.

Main Methods:

• Domain-swapping experiments were conducted between skcg-SK and SK2b-cluster streptokinase variants.
• Functional characteristics including proteolytic activity, fibrinogen-bound plasminogen activation, and α2-antiplasmin resistance were assessed.

Main Results:

• The SKβ domain plays a significant role in the diverse functionalities of skcg-SK and SK2b streptokinase variants.
• Specific critical residues within SKβ may act as 'hot spots' influencing these functions.
• Results indicate a minor to determining role for SKβ across tested functionalities.

Conclusions:

• The SKβ domain is crucial for various streptokinase functions, with specific residues acting as key determinants.
• Findings deepen the understanding of SKβ's role in different streptokinase clusters.
• This knowledge may facilitate the engineering of more effective and safer fibrin-specific streptokinase variants for treating blood clots.