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A kinetic study of human IgG binding to placental Fc gamma-receptor
1Department of Chemical Pathology, Leicester Royal Infirmary, U.K.
Various methods for studying the IgG interaction with its placental receptor have been examined to establish kinetic parameters. IgG binding has an average rate constant k1 of (2.57 +/- 0.94) x 10(7)/M per min. However, high displacement doses (1000 micrograms) of unlabelled IgG resulted in a curvilinear dissociation curve with two binding sites: one with a fast dissociation rate constant, k2 of 0.100/min and a slow one with k2 of 0.010/min. IgG binding was associated with a high average affinity of (3.70 +/- 1.65) x 10(8)/M and a total number of receptor binding sites of (2.07 +/- 0.93) x 10(14) sites/mg of membrane protein, in close agreement with previous results. The stoichiometry of IgG to Fc gamma-receptor was established as a 4:1 binding ratio from log dose-response curves as opposed to a 1:1 binding ratio from previous reports.
Various methods for studying the IgG interaction with its placental receptor have been examined to establish kinetic parameters. IgG binding has an average rate constant k1 of (2.57 +/- 0.94) x 10(7)/M per min. However, high displacement doses (1000 micrograms) of unlabelled IgG resulted in a curvilinear dissociation curve with two binding sites: one with a fast dissociation rate constant, k2 of 0.100/min and a slow one with k2 of 0.010/min. IgG binding was associated with a high average affinity of (3.70 +/- 1.65) x 10(8)/M and a total number of receptor binding sites of (2.07 +/- 0.93) x 10(14) sites/mg of membrane protein, in close agreement with previous results. The stoichiometry of IgG to Fc gamma-receptor was established as a 4:1 binding ratio from log dose-response curves as opposed to a 1:1 binding ratio from previous reports.