A functional model of the human C1 complex Emergence of a functional model.

Precise structural data on C1s-C1r-C1r-C1s, the catalytic subunit of C1 (the first component of the classical pathway of human complement), led to the emergence of a structural and functional model of this complex protease. Now with new structural information on the amino acid sequence of the protease responsible for C1 activation (C1r), Gérard Arlaud and his colleagues propose a refinement of their original C1 model, and an overall scheme of the intramolecular events associated with the activation and control of C1.