The covalent differences between bovine alpha- and beta-thrombin. A structural explanation for the changes in...

Area of Science:

• Biochemistry
• Molecular Biology
• Proteomics

Background:

• Thrombin is a key enzyme in blood coagulation.
• Understanding thrombin's structure is crucial for developing anticoagulants.
• Bovine beta-thrombin is a modified form of alpha-thrombin with altered activity.

Purpose of the Study:

• To determine the partial covalent structure of bovine beta-thrombin.
• To elucidate the fragmentation pattern of alpha-thrombin leading to beta-thrombin.
• To identify the linkages between the polypeptide chains in beta-thrombin.

Main Methods:

• Automated Edman degradation for peptide sequencing.
• Carboxypeptidase digestion to identify C-terminal residues.
• Gel filtration for polypeptide chain separation.
• Reduction and carboxymethylation or performic acid oxidation for disulfide bond analysis.

Main Results:

• Bovine beta-thrombin consists of three peptide chains originating from alpha-thrombin proteolysis.
• An A1 chain (17 amino acids) and a B2 chain are linked by a disulfide bridge.
• A B1 chain is non-covalently associated with the B2-A1 complex, requiring denaturing conditions for separation.

Conclusions:

• The structure of beta-thrombin involves specific proteolytic cleavage of alpha-thrombin.
• Disulfide bonds and strong non-covalent interactions stabilize the beta-thrombin structure.
• These findings contribute to understanding thrombin's structure-function relationship.