Mutational Analyses of the Recombinant Globular Regions of Human C1q A, B, and C Chains Suggest an Essential Role for Arginine and Histidine Residues in the C1q-IgG Interaction

Abstract excerpt

The first step in the activation of the classical complement pathway by immune complexes involves the binding of the globular domain (gC1q) of C1q to the Fc regions of aggregated IgG or IgM. Each gC1q domain is a heterotrimer of the C-terminal halves of one A (ghA), one B (ghB), and one C (ghC) chain. Our recent studies have suggested a modular organization of gC1q, consistent with the view that ghA, ghB, and ghC...