Bovine factor X1 (Stuart factor). Primary structure of the light chain

Area of Science:

• Biochemistry
• Molecular Biology
• Proteomics

Background:

• Bovine factor X1 is a key protein in blood coagulation.
• Understanding protein structure is crucial for elucidating function.
• Unusual amino acids can significantly impact protein properties.

Purpose of the Study:

• To determine the complete amino acid sequence of the bovine factor X1 light chain.
• To investigate the structural relationship between factor X1 and prothrombin.
• To explore the implications of lambda-carboxy-glutamic acid in calcium binding.

Main Methods:

• Automated sequencing of protein fragments generated by specific enzymatic cleavage (arginyl, glutamyl, tryptophanyl, asparaginyl-glycine bonds).
• Conventional sequencing methods for remaining residues.
• Comparative sequence analysis.

Main Results:

• The complete 140-residue amino acid sequence of the bovine factor X1 light chain was determined.
• The amino-terminal sequence exhibits homology with bovine prothrombin.
• The sequence contains residues of lambda-carboxy-glutamic acid, an unusual amino acid.

Conclusions:

• The structural homology suggests a shared evolutionary origin or functional relationship between factor X1 and prothrombin.
• The presence of lambda-carboxy-glutamic acid is implicated in the calcium-binding capabilities of both factor X1 and prothrombin.
• Further research is warranted to fully understand the functional significance of this unusual amino acid in coagulation factors.