Abstract
The role of histidine residue in the surface binding and autoactivation of human factor XII has been investigated by chemical modification with diethyl pyrocarbonate. It is found that low concentrations of diethyl pyrocarbonate have profound inhibitory effects on the surface binding activity of factor XII. At 2.5-fold molar excess of the reagent, six histidines are modified and 80% of the amidolytic activity is lost. Electrophoretic studies show that the modified protein has lost the capacity to bind to the surface, resulting in diminished proteolytic autoactivation. When modification is performed in the presence of the surface, dextran sulfate, two of the six histidines are protected from modification and the amidolytic activity is completely preserved. It is concluded that histidine residues in factor XII play key role in its surface binding activity.
Published Version
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