Membrane Attack Complex / MAC: Complement Component C9

Membrane Attack Complex / MAC: Complement Component C9

Membrane Attack Complex / MAC: Complement Component C9 Background

Complement component C9 is a multi-domain protein that contains an N-terminal type-1 TSP domain, an LDL-receptor class A repeat, a number of potential transmembrane (TM) regions and a C-terminal EGF-like domain. The membrane attack complex (MAC)/perforin-like protein complement component 9 (C9) is the major component of the MAC, a multi-protein complex that forms pores in the membrane of target pathogens. In contrast to homologous proteins such as perforin and the cholesterol-dependent cytolysins (CDCs), all of which require the membrane for oligomerisation, C9 assembles directly onto the nascent MAC from solution.

Membrane Attack Complex / MAC: Complement Component C9 Deficiency

Complement component C9 deficiency is inherited as an autosomal recessive trait and it results in inability to assemble the MAC with a subsequent increased susceptiblity to infection. Serum from C9-deficient individuals is able to kill meningococci but at a slower rate than normal control serum. The risk of developing meningococcal disease among C9-deficient individuals is 700-fold greater than that in Japanese individuals with no complement deficiency.

Membrane Attack Complex / MAC: Complement Component C9 References

1. Dudkina N V, et al. (2016). Structure of the poly-C9 component of the complement membrane attack complex. Nature communications, 7.
2. Kang H J, et al. (2005). High incidence of complement C9 deficiency in Koreans. Annals of Clinical & Laboratory Science, 35(2), 144-148.