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A novel prothrombin activator from the venom of Micropechis ikaheka: isolation and characterization
Rong Gao1, R Manjunatha Kini, P Gopalakrishnakone
1Venom and Toxin Research Programme, Department of Anatomy, Faculty of Medicine, National University of Singapore, 10 Kent Ridge Crescent, 119260, Singapore, Singapore.
Abstract:
A novel prothrombin activator, Mikarin, has been isolated from Micropechis ikaheka venom. It is a single polypeptide chain metalloproteinase with the apparent molecular weight of 47kDa. Mikarin exhibits Ca(2+)-independent prothrombin activation, but no effects on other blood coagulation factors, such as factor X and fibrinogen. Mikarin is the first member of group I prothrombin activators from elapid venom. Like other high-molecular-weight snake venom proteinases, it has three structural domains, metalloproteinase and disintegrin-like and Cys-rich domains, and belongs to the P-III class of snake venom metalloproteinases. The N-terminal of Mikarin exhibits 76% sequence identity with Cobrin, a metalloproteinase identified from Naja naja venom, but very lower identities were found when compared with those from viperid and crotalid venom. In addition, the presence of disintegrin-like and Cys-rich domains in snake venom metalloproteinases with diverse biological activities suggests that these domains may be important for their function.
Insights
A novel snake venom protein, Mikarin, activates prothrombin independently of calcium. This metalloproteinase from elapid venom offers new insights into coagulation factor regulation.
Area of Science:
- Biochemistry
- Toxicology
- Molecular Biology
Background:
- Snake venom contains diverse bioactive proteins, including metalloproteinases.
- Prothrombin activators are crucial enzymes in the coagulation cascade.
- Elapid venoms represent a rich source of novel enzymes with potential biomedical applications.
Purpose of the Study:
- To isolate and characterize a novel prothrombin activator from Micropechis ikaheka venom.
- To determine the enzymatic activity and structural properties of the novel activator.
- To classify the activator within the known families of snake venom metalloproteinases.
Main Methods:
- Isolation and purification of Mikarin from Micropechis ikaheka venom.
- Determination of molecular weight using SDS-PAGE.
- Assay of prothrombin activation and effects on other coagulation factors (Factor X, fibrinogen).
- Analysis of protein domains and N-terminal sequence identity.
Main Results:
- A novel metalloproteinase, Mikarin, was isolated, with a molecular weight of 47kDa.
- Mikarin demonstrated calcium-independent prothrombin activation.
- No significant activity was observed on Factor X or fibrinogen.
- Mikarin possesses metalloproteinase, disintegrin-like, and Cys-rich domains, classifying it as a P-III class metalloproteinase.
- High sequence identity was found with Cobrin from Naja naja venom.
Conclusions:
- Mikarin is the first Group I prothrombin activator identified from elapid venom.
- The structural domains (disintegrin-like, Cys-rich) may contribute to the diverse functions of snake venom metalloproteinases.
- Mikarin represents a valuable tool for studying the coagulation cascade and holds potential for therapeutic development.