Complement C9 is inserted into membranes in a globular conformation

Abstract
Complement component C9 undergoes a major conformational change during its insertion into a biological membrane from a globular to an extended form. At 0°C a single C9 binds but a membrane attack complex (MAC) is not formed. We show that the C9 bound at 0°C is accessible to the intracellular space and sensitive to trypsin digestion, suggesting that C9 inserts in its globular state and requires an elevated temperature in order to change conformation. Complement; C9; Membrane assembly; Cytotoxicity