The immunoglobulin-binding activity of subcomponent Clq of human complement is lost following treatment with diethylpyrocarbonate; the inactivation showed first-order kinetics with respect to time and modifier concentration. Soluble IgG oligomers protected Clq against diethylpyrocarbonate modification. Treatment of modified Clq with hydroxylamine resulted in an 85% recovery of its ability to bind to aggregated immuno-globulin. The inactivation process was associated with modification of 12.1±0.7 histidine residues per Clq molecule. These data are consistent with the presence of histidine residues in the immunoglobulin-binding sites of Clq; these residues may participate in ionic interactions with the carboxyl groups known to be in the Clq binding site of IgG.
Research Article| February 01 1983
Evidence for histidine residues in the immunoglobulin-binding site of human C1q
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S. B. Easterbrook-Smith; Evidence for histidine residues in the immunoglobulin-binding site of human C1q. Biosci Rep 1 February 1983; 3 (2): 135–140. doi: https://doi.org/10.1007/BF01121944
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