Feb 15, 1983

Localization of the disulfide bond in human antithrombin III required for heparin-accelerated thrombin inactivation

Archives of Biochemistry and Biophysics
W S Ferguson, T H Finlay


Heparin accelerates the rate of inhibition of thrombin by antithrombin III. Reduction of one of the three antithrombin disulfide bonds with dithiothreitol under mild conditions abolishes this rate-enhancing effect without affecting the rate of reaction in the absence of heparin. Alkylation of mildly reduced antithrombin III with [3H]iodacetic acid followed by digestion with cyanogen bromide yielded two major labeled peptides. The smaller peptide, containing Cys-422, was identified as extending from Gly-414 to the C-terminus, Lys-424. Our data are consistent with the larger labeled peptide being the one extending from Glu-104 to Met-243 and containing Cys-239. Cys-422 has been shown by others to be linked to Cys-239. These data indicate that the sensitive disulfide bond in antithrombin III extends between Cys-239 and Cys-422; the site at which thrombin cleaves the antithrombin III is between these two half-cystines.

Mentioned in this Paper

Establishment and Maintenance of Localization
Antithrombin III, Human
F2 gene
Bromides Measurement
High Pressure Liquid Chromatography Procedure

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