Background
As part of the innate immune system, the complement system is made up of a large number of proteins that are essential for the control of common bacterial infections and elicit a series of inflammatory responses by mediates innate immunity through a complement cascade procedure. This system is activated through three pathways, the classical pathway, the alternative pathway, and the lectin complement pathway. The activation of three pathway results in the formation of the C5 convertase, which in turn cleaves C5 into C5a and C5b to initiate the formation of the terminal complement complex (TCC) at the targeted site sequentially together with C5b, C6, C7, C8 and C9, which is also called as the membrane attack complex (MAC). Assembly of the MAC on target cells results in the formation of transmembrane pores that can lead to the killing of the cells, which is the signature feature of complement.
Complement Component C7
C7 is one of five precursor proteins of the MAC of complement. C7 is a mosaic protein that is composed of 821 amino acid residues, which is a single-chain glycoprotein consisting of 240 amino acids of a single domain (MACPF) and eight cysteine-rich modules of about each 34-75 amino acids. C7 is structurally and biochemically similar to the other terminal complement proteins, C6, C8, and C9, and interacts with each other to represent a functional unit. During the process of MAC formation, C7 plays a significant role in bringing about the hydrophilic-amphiphilic transition and binds to the C5b and C6 forming a trimolecular complex C5b-7 which resembles an integral membrane protein and serves as an anchor for the late complement components, C8 and C9. Mutations in the C7 gene cause C7 deficiency, a defect associated with increased susceptibility to neisserial recurrent infections. Variants of C7 are associated with immunodeficiency diseases and susceptibility to infection, such as meningococcal disease caused by Neisseria meningitidis.
Fig. 1 Complement C7 participates in the MAC assembly.1
Complement Component C7 Based Therapy
Individuals with inherited deficiencies of the terminal components of the complement system frequently suffer from recurrent systemic infections caused by Neisseria meningitidis or Neisseria gonorrhoeae, including meningococcal meningitis, meningococcemia, and disseminated gonococcal infection. One major endpoint of complement activation is the formation of the MAC, which is responsible for the cytolytic function of the complement system and contributes to the innate defense against pathogens. Deficiencies in terminal complement components (C6-C9), including the complement C7, are uncommon and prevents the formation of a functional MAC, though it is associated with enhanced susceptibility to systemic neisserial infection but does not cause severe immunodeficiency. Creative Biolabs offers high-quality anti-complement C7 antibodies, recombinant complement C7 proteins, complement C7 ELISA kits, complement C7 peptides, C7 protein lysate from 293T cell, and C7 drug development for the treatment of a range of different diseases caused by uncontrolled activation of the complement system.
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Reference
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Bubeck, D., et al. "Structural basis for membrane attack complex inhibition by CD59." (2023).
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