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Analysis of binding sites on complement factor I using artificial N-linked glycosylation.

Sánchez Gallego, José Ignacio LU ; Groeneveld, Tom; Krentz, Stefanie; Nilsson, Sara LU ; Villoutreix, Bruno O and Blom, Anna LU (2012) In Journal of Biological Chemistry 287(17). p.13572-13583
Abstract
Factor I (FI) is a serine protease that inhibits all complement pathways by degrading activated complement components C3b and C4b. FI functions only in the presence of several cofactors such as factor H, C4b-binding protein, complement receptor 1 and membrane cofactor protein. FI is composed of two chains linked by a disulphide bridge; the light chain comprises only the serine protease (SP) domain, while the heavy chain contains FI membrane attack complex domain (FIMAC), CD5 domain, low-density lipoprotein receptor 1 (LDLr1) and LDLr2 domains. To better understand how FI inhibits complement, we used homology-based 3D models of FI domains in an attempt to identify potential protein-protein interaction sites. Specific amino acids were then... (More)
Factor I (FI) is a serine protease that inhibits all complement pathways by degrading activated complement components C3b and C4b. FI functions only in the presence of several cofactors such as factor H, C4b-binding protein, complement receptor 1 and membrane cofactor protein. FI is composed of two chains linked by a disulphide bridge; the light chain comprises only the serine protease (SP) domain, while the heavy chain contains FI membrane attack complex domain (FIMAC), CD5 domain, low-density lipoprotein receptor 1 (LDLr1) and LDLr2 domains. To better understand how FI inhibits complement, we used homology-based 3D models of FI domains in an attempt to identify potential protein-protein interaction sites. Specific amino acids were then mutated to yield 20 recombinant mutants of FI carrying additional surface exposed N-glycosylation sites that were expected to sterically hinder interactions. The Michaelis constant (Km) of all FI mutants toward a small substrate was not increased. We found that many mutations in the FIMAC and SP domains nearly abolished ability of FI to degrade C4b and C3b in the fluid phase and on the surface, irrespectively of the cofactor used. In the other hand only few alterations in the CD5 and LDLr1/2 domains impaired this activity. In conclusion, all analyzed cofactors form similar trimolecular complexes with FI and C3b/C4b, and the accessibility of FIMAC and SP domains is crucial for the function of FI. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Journal of Biological Chemistry
volume
287
issue
17
pages
13572 - 13583
publisher
ASBMB
external identifiers
  • wos:000303996300014
  • pmid:22393059
  • scopus:84859941703
ISSN
1083-351X
DOI
10.1074/jbc.M111.326298
language
English
LU publication?
yes
id
e66e4fb5-0de4-4872-80cc-63b3482a54b8 (old id 2432208)
alternative location
http://www.ncbi.nlm.nih.gov/pubmed/22393059?dopt=Abstract
date added to LUP
2012-04-03 08:52:29
date last changed
2017-10-01 03:24:35
@article{e66e4fb5-0de4-4872-80cc-63b3482a54b8,
  abstract     = {Factor I (FI) is a serine protease that inhibits all complement pathways by degrading activated complement components C3b and C4b. FI functions only in the presence of several cofactors such as factor H, C4b-binding protein, complement receptor 1 and membrane cofactor protein. FI is composed of two chains linked by a disulphide bridge; the light chain comprises only the serine protease (SP) domain, while the heavy chain contains FI membrane attack complex domain (FIMAC), CD5 domain, low-density lipoprotein receptor 1 (LDLr1) and LDLr2 domains. To better understand how FI inhibits complement, we used homology-based 3D models of FI domains in an attempt to identify potential protein-protein interaction sites. Specific amino acids were then mutated to yield 20 recombinant mutants of FI carrying additional surface exposed N-glycosylation sites that were expected to sterically hinder interactions. The Michaelis constant (Km) of all FI mutants toward a small substrate was not increased. We found that many mutations in the FIMAC and SP domains nearly abolished ability of FI to degrade C4b and C3b in the fluid phase and on the surface, irrespectively of the cofactor used. In the other hand only few alterations in the CD5 and LDLr1/2 domains impaired this activity. In conclusion, all analyzed cofactors form similar trimolecular complexes with FI and C3b/C4b, and the accessibility of FIMAC and SP domains is crucial for the function of FI.},
  author       = {Sánchez Gallego, José Ignacio and Groeneveld, Tom and Krentz, Stefanie and Nilsson, Sara and Villoutreix, Bruno O and Blom, Anna},
  issn         = {1083-351X},
  language     = {eng},
  number       = {17},
  pages        = {13572--13583},
  publisher    = {ASBMB},
  series       = {Journal of Biological Chemistry},
  title        = {Analysis of binding sites on complement factor I using artificial N-linked glycosylation.},
  url          = {http://dx.doi.org/10.1074/jbc.M111.326298},
  volume       = {287},
  year         = {2012},
}