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NMR Structure of C345C (NTR) domain of C5 of complement
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). Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedThe complement protein C5 initiates assembly of the membrane attack complex. This remarkable process results in lysis of target cells and is fundamental to mammalian defense against infection. The 150-amino acid residue domain at the C terminus of C5 (C5-C345C) is pivotal to C5 function. It interacts with enzymes that convert C5 to C5b, the first step in the assembly of the membrane attack complex; it also binds to the membrane attack complex components C6 and C7 with high affinity. Here a recombinant version of this C5-C345C domain is shown to adopt the oligosaccharide/oligonucleotide binding fold, with two helices packed against a five-stranded beta-barrel. The structure is compared with those from the netrin-like module family that have a similar fold. Residues critical to the interaction with C5-convertase cluster on a mobile, hydrophobic inter-strand loop that protrudes from the open face of the beta-barrel. The opposite, helix-dominated face of C5-C345C carries a pair of exposed hydrophobic side chains adjacent to a striking negatively charged patch, consistent with affinity for positively charged factor I modules in C6 and C7. Modeling of homologous domains from complement proteins C3 and C4, which do not participate in membrane attack complex assembly, suggests that this provisionally identified C6/C7-interacting face is indeed specific to C5. Functional insights from the structure of the multifunctional C345C domain of C5 of complement.,Bramham J, Thai CT, Soares DC, Uhrin D, Ogata RT, Barlow PN J Biol Chem. 2005 Mar 18;280(11):10636-45. Epub 2004 Dec 14. PMID:15598652[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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