Interaction between the Labile Binding Site of Human C4 and Methylamine

Abstract

Human complement component C4 was irreversibly inactivated by low concentrations of methylamine at slightly alkaline pH. The inactivated C4 molecules lost the ability to bind to EACT [erythrocyte-antibody-Cl complexed] cells but retained the capacity to participate in the formation of classical pathway C3 convertase in the fluid phase. 14C-methylamine was incorporated into the .alpha.-chain at a ratio of 1 mole methylamine per mole C4.