A mechanism for the insertion of complement component C9 into target membranes

Complement component C9 is a globular serum protein which can insert and polymerise in a target membrane to form a large membrane channel. The ability to insert in the membrane is conferred by amphipathetic elements of secondary structure in the central part of the molecule. Towards each end high cysteine domains are found, one of which is homologous to the apoprotein binding domains of the LDL receptor. From the sequence and topological data for C9 we present a model for its structure and insertion into the membrane.