Heparin binding defect in a new antithrombin III variant: Rouen, 47 Arg to His.
Antithrombin III (AT-III) Rouen is a hereditary abnormal antithrombin with normal progressive inhibitory activity and reduced heparin cofactor activity. It was isolated from the plasma of a woman who suffered a sudden idiopathic sensorineural hearing loss and balance impairment. There was no familial history of thrombosis. By heparin-Sepharose chromatography, AT-III Rouen was separated from the normal antithrombin on elution with increasing concentrations of NaCl. AT-III Rouen eluted earlier than is normal at both pH 7.4 and pH 6.0. At the lower pH, the antithrombins bound more avidly to the column, with the abnormal AT-III eluting closer to the normal than at the higher pH. Two-dimensional peptide mapping of tryptic and Staphylococcus aureus V8 protease digests of carboxymethylated antithrombins was performed on thin-layer silica plates. The abnormal peptide was located by tryptophan staining, and amino acid analysis and sequence studies demonstrated a substitution of an arginine at residue 47 for a histidine. Results from this study suggest that replacement of arginine 47 by a partially positively charged histidine has less effect on the heparin binding affinity than dose replacing it with a neutral cysteine side chain as in AT-III Toyama, in which no heparin binding was observed. In addition, heparin binding per se is not a sufficient condition to activate AT-III.
D000328:Adult; D000595:Amino Acid Sequence; D000990:Antithrombin III / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D001120:Arginine / Q000502:physiology; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D014644:Genetic Variation; D006493:Heparin / Q000378:metabolism*; D006639:Histidine / Q000502:physiology; D006801:Humans; D010449:Peptide Mapping; D011485:Protein Binding
C052332:antithrombin III Rouen; D006639:Histidine; D000990:Antithrombin III; D006493:Heparin; D001120:Arginine