Related Experiment Video
Updated: Apr 4, 2026
Author Spotlight: Affinity Purification of a Fibrinolytic Enzyme from Sipunculus nudus
Published on: June 2, 2023
Crystal Structure of the Michaelis Complex between Tissue-type Plasminogen Activator and Plasminogen Activators
Lihu Gong1, Min Liu1, Tu Zeng2
1From the State Key Laboratory of Structural Chemistry and Danish-Chinese Centre for Proteases and Cancer, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, 350002 Fujian, China, the University of Chinese Academy of Sciences, Beijing, 100049, China, and.
Abstract:
Thrombosis is a leading cause of death worldwide. Recombinant tissue-type plasminogen activator (tPA) is the Food and Drug Administration-approved thrombolytic drug. tPA is rapidly inactivated by endogenous plasminogen activator inhibitor-1 (PAI-1). Engineering on tPA to reduce its inhibition by PAI-1 without compromising its thrombolytic effect is a continuous effort. Precise details, with atomic resolution, of the molecular interactions between tPA and PAI-1 remain unknown despite previous extensive studies. Here, we report the crystal structure of the tPA·PAI-1 Michaelis complex, which shows significant differences from the structure of its urokinase-type plasminogen activator analogue, the uPA·PAI-1 Michaelis complex. The PAI-1 reactive center loop adopts a unique kinked conformation. The structure provides detailed interactions between tPA 37- and 60-loops with PAI-1. On the tPA side, the S2 and S1β pockets open up to accommodate PAI-1. This study provides structural basis to understand the specificity of PAI-1 and to design newer generation of thrombolytic agents with reduced PAI-1 inactivation.
Insights
Researchers revealed the crystal structure of tissue-type plasminogen activator (tPA) bound to plasminogen activator inhibitor-1 (PAI-1). This finding clarifies molecular interactions, aiding the design of improved thrombolytic drugs with reduced PAI-1 inactivation.
Area of Science:
- Biochemistry
- Structural Biology
- Pharmacology
Background:
- Thrombosis is a major global health threat, necessitating effective thrombolytic therapies.
- Recombinant tissue-type plasminogen activator (tPA) is an FDA-approved drug for treating thrombosis.
- Endogenous plasminogen activator inhibitor-1 (PAI-1) rapidly inactivates tPA, limiting its therapeutic efficacy.
Purpose of the Study:
- To elucidate the precise molecular interactions between tPA and PAI-1 at atomic resolution.
- To understand the structural basis for PAI-1's specificity towards tPA.
- To provide insights for designing next-generation thrombolytic agents with enhanced PAI-1 resistance.
Main Methods:
- X-ray crystallography was employed to determine the structure of the tPA·PAI-1 Michaelis complex.
- Comparative structural analysis with the uPA·PAI-1 complex was performed.
- Detailed examination of molecular contacts between tPA loops and PAI-1 was conducted.
Main Results:
- The crystal structure of the tPA·PAI-1 Michaelis complex was determined, revealing unique features.
- Significant structural differences were observed compared to the uPA·PAI-1 complex.
- The PAI-1 reactive center loop adopted a distinct kinked conformation.
- Specific interactions involving tPA 37- and 60-loops with PAI-1 were identified.
- The tPA S2 and S1β pockets were found to accommodate PAI-1.
Conclusions:
- The determined structure provides unprecedented atomic-level detail of the tPA·PAI-1 interaction.
- This structural information is crucial for understanding PAI-1 specificity.
- The findings lay the groundwork for engineering tPA variants with reduced PAI-1 inactivation for improved thrombolytic therapy.
Related Concept Videos
01:16Clot Retraction and Fibrinolysis
01:09Cytoskeletal Linker Proteins - Plakins