Abstract
A genetic variant of antithrombin with impaired heparin cofactor activity was identified in 4 members of a French family. Both the variant and normal antithrombin component were purified by affinity chromatography on heparin Sepharose. Reverse phase peptide mapping revealed a single altered peak when tryptic digests of both antithrombins were compared. After further purification of the aberrant peptide, amino acid analysis indicated a substitution of 41 Leu+Pro (antithrombin Basel). This result was confirmed by liquid secondary ion mass spectrometry which gave a measured mass of 81 6.4655 Da for the new peptide compared to a calculated mass of 800.3579 Da for the normal peptide and 816. 4579 for the Leu-Pro substitution.