erythro-beta-Hydroxyaspartic acid in bovine factor IX and factor X

Area of Science:

• Biochemistry
• Proteomics

Background:

• Factor IX and Factor X are crucial blood coagulation proteins.
• Understanding post-translational modifications like beta-hydroxyaspartic acid is vital for protein function.

Purpose of the Study:

• To precisely localize beta-hydroxyaspartic acid within human Factor IX and Factor X.
• To confirm the specific positions of this modification in both proteins.

Main Methods:

• Proteolytic cleavage of Factor IX (cyanogen bromide) and Factor X (trypsin).
• Isolation of peptides containing beta-hydroxyaspartic acid.
• Edman degradation and High-Performance Liquid Chromatography (HPLC) for phenylthiohydantoin derivative identification.
• Confirmation using subtractive Edman degradation and the dansyl method.

Main Results:

• Beta-hydroxyaspartic acid was identified at position 3 in the Factor IX fragment.
• Beta-hydroxyaspartic acid was identified at position 1 in the Factor X fragment.
• These positions correspond to residue 64 in Factor IX and residue 63 in the light chain of Factor X.

Conclusions:

• The study successfully localized beta-hydroxyaspartic acid in Factor IX and Factor X.
• Provides precise positional data for this post-translational modification in key coagulation factors.