[Study of the role of histidine residues in streptokinase molecule using modification with diethylpyrocarbonate].

The interaction of streptokinase with diethylpyrocarbonate resulting in partial inactivation of the protein was studied. Eight histidine residues are blocked per streptokinase molecule by this reagent. Ethoxyformylation of streptokinase histidyls is characterized by a rate constant corresponding to modification of free L-histidine. No reactivation of streptokinase was achieved by treatment of the modified protein with hydroxylamine. The CD spectroscopy data suggest that the residues modified by diethylpyrocarbonate are of no consequence for the stabilization of the protein secondary structure. The specificity of modification of streptokinase histidine residues by diethylpyrocarbonate is discussed. Based on the gel chromatography data, it was assumed that partial inactivation of streptokinase depends on the formation of protein oligomers with a decreased activatory function.