9t6j
Complement C5 re-refined
Structural highlights
DiseaseCO5_HUMAN Defects in C5 are the cause of complement component 5 deficiency (C5D) [MIM:609536. A rare defect of the complement classical pathway associated with susceptibility to severe recurrent infections, predominantly by Neisseria gonorrhoeae or Neisseria meningitidis. Note=An association study of C5 haplotypes and genotypes in individuals with chronic hepatitis C virus infection shows that individuals homozygous for the C5_1 haplotype have a significantly higher stage of liver fibrosis than individuals carrying at least 1 other allele (PubMed:15995705). FunctionCO5_HUMAN Activation of C5 by a C5 convertase initiates the spontaneous assembly of the late complement components, C5-C9, into the membrane attack complex. C5b has a transient binding site for C6. The C5b-C6 complex is the foundation upon which the lytic complex is assembled. Derived from proteolytic degradation of complement C5, C5 anaphylatoxin is a mediator of local inflammatory process. It induces the contraction of smooth muscle, increases vascular permeability and causes histamine release from mast cells and basophilic leukocytes. C5a also stimulates the locomotion of polymorphonuclear leukocytes (chemokinesis) and direct their migration toward sites of inflammation (chemotaxis). Publication Abstract from PubMedTo provide insight into the structural and functional properties of human complement component 5 (C5), we determined its crystal structure at a resolution of 3.1 A. The core of C5 adopted a structure resembling that of C3, with the domain arrangement at the position corresponding to the C3 thioester being very well conserved. However, in contrast to C3, the convertase cleavage site in C5 was ordered and the C345C domain flexibly attached to the core of C5. Binding of the tick C5 inhibitor OmCI to C5 resulted in stabilization of the global conformation of C5 but did not block the convertase cleavage site. The structure of C5 may render possible a structure-based approach for the design of new selective complement inhibitors. Structure of and influence of a tick complement inhibitor on human complement component 5.,Fredslund F, Laursen NS, Roversi P, Jenner L, Oliveira CL, Pedersen JS, Nunn MA, Lea SM, Discipio R, Sottrup-Jensen L, Andersen GR Nat Immunol. 2008 Jul;9(7):753-60. Epub 2008 Jun 8. PMID:18536718[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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