Structural highlights
Disease
CO5_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).
Function
CO5_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 PubMed
The serum glycoprotein C5a, which is derived from the proteolytic cleavage of complement protein C5, has been implicated in the pathogenesis of a number of inflammatory and allergic conditions. Because C5a induces an inflammatory response upon binding to a specific receptor, structural and mutagenesis studies were carried out to gain a better understanding of this binding interaction. These studies led to the first structural definition of the C terminus of recombinant human (rh)-C5a, determined by two-dimensional nuclear magnetic resonance (NMR) spectroscopy. Our results show that the C terminus adopts an alpha-helical conformation spanning residues 69 to 74, while the core domain exists as an antiparallel alpha-helical bundle. This C-terminal helix is connected to the core by a short loop that orients Arg 74 adjacent to Arg 62. Point mutation analysis had already revealed that residues 62 and 74 significantly contribute to agonist activity and receptor binding. Correlation of the C5a tertiary structure with mutational analyses clarifies the significance of the functional and binding properties of Arg 62 and suggests that both Arg 62 and Arg 74 interact at the same binding site on the receptor.
Structural definition of the C5a C terminus by two-dimensional nuclear magnetic resonance spectroscopy.,Zhang X, Boyar W, Toth MJ, Wennogle L, Gonnella NC Proteins. 1997 Jun;28(2):261-7. PMID:9188742[1]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
See Also
References
- ↑ Zhang X, Boyar W, Toth MJ, Wennogle L, Gonnella NC. Structural definition of the C5a C terminus by two-dimensional nuclear magnetic resonance spectroscopy. Proteins. 1997 Jun;28(2):261-7. PMID:9188742
