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Analysis of binding sites on complement factor I that are required for its activity.

Nilsson, Sara LU ; Nita, Izabela LU ; Walther, Lisa LU ; Groeneveld, Tom LU ; Trouw, Leendert LU ; Villoutreix, Bruno O and Blom, Anna LU (2010) In Journal of Biological Chemistry 285. p.6235-6245
Abstract
The central complement inhibitor factor I (FI) degrades activated complement factors C4b and C3b in the presence of cofactors such as C4b-binding protein, factor H, complement receptor 1 and membrane cofactor protein. FI is a serine protease composed of two chains; the light chain comprises the serine protease domain, while the heavy chain contains several domains: the FI and membrane attack complex domain (FIMAC), CD5, low density lipoprotein receptor 1 (LDLr1) and LDLr2 domains. In order to understand better how FI acts as a complement inhibitor, we used homology-based models of FI domains to predict potential binding sites. Specific amino acids were then mutated to yield 16 well-expressed mutants, which were then purified from media of... (More)
The central complement inhibitor factor I (FI) degrades activated complement factors C4b and C3b in the presence of cofactors such as C4b-binding protein, factor H, complement receptor 1 and membrane cofactor protein. FI is a serine protease composed of two chains; the light chain comprises the serine protease domain, while the heavy chain contains several domains: the FI and membrane attack complex domain (FIMAC), CD5, low density lipoprotein receptor 1 (LDLr1) and LDLr2 domains. In order to understand better how FI acts as a complement inhibitor, we used homology-based models of FI domains to predict potential binding sites. Specific amino acids were then mutated to yield 16 well-expressed mutants, which were then purified from media of eukaryotic cells for functional analyses. The Michaelis constant (Km) of all FI mutants towards a small substrate was not altered while some mutants showed increased maximum initial velocity (Vmax). All the mutations in the FIMAC domain affected the ability of FI to degrade C4b and C3b irrespective of the cofactor used whereas only some mutations in the CD5 and LDLr1/2 domains had similar effect. These same mutants also showed impaired binding to C3met. In conclusion, the FIMAC domain appears to harbor the main binding sites important for the ability of FI to degrade C4b and C3b. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Journal of Biological Chemistry
volume
285
pages
6235 - 6245
publisher
American Society for Biochemistry and Molecular Biology
external identifiers
  • WOS:000275367500028
  • PMID:20044478
  • Scopus:77949909418
ISSN
1083-351X
DOI
10.1074/jbc.M109.097212
language
English
LU publication?
yes
id
0bafbf1d-2493-4c4b-bc39-00806d3e3bf9 (old id 1541415)
alternative location
http://www.ncbi.nlm.nih.gov/pubmed/20044478?dopt=Abstract
date added to LUP
2010-02-02 11:40:04
date last changed
2016-10-13 04:23:05
@misc{0bafbf1d-2493-4c4b-bc39-00806d3e3bf9,
  abstract     = {The central complement inhibitor factor I (FI) degrades activated complement factors C4b and C3b in the presence of cofactors such as C4b-binding protein, factor H, complement receptor 1 and membrane cofactor protein. FI is a serine protease composed of two chains; the light chain comprises the serine protease domain, while the heavy chain contains several domains: the FI and membrane attack complex domain (FIMAC), CD5, low density lipoprotein receptor 1 (LDLr1) and LDLr2 domains. In order to understand better how FI acts as a complement inhibitor, we used homology-based models of FI domains to predict potential binding sites. Specific amino acids were then mutated to yield 16 well-expressed mutants, which were then purified from media of eukaryotic cells for functional analyses. The Michaelis constant (Km) of all FI mutants towards a small substrate was not altered while some mutants showed increased maximum initial velocity (Vmax). All the mutations in the FIMAC domain affected the ability of FI to degrade C4b and C3b irrespective of the cofactor used whereas only some mutations in the CD5 and LDLr1/2 domains had similar effect. These same mutants also showed impaired binding to C3met. In conclusion, the FIMAC domain appears to harbor the main binding sites important for the ability of FI to degrade C4b and C3b.},
  author       = {Nilsson, Sara and Nita, Izabela and Walther, Lisa and Groeneveld, Tom and Trouw, Leendert and Villoutreix, Bruno O and Blom, Anna},
  issn         = {1083-351X},
  language     = {eng},
  pages        = {6235--6245},
  publisher    = {ARRAY(0x9760660)},
  series       = {Journal of Biological Chemistry},
  title        = {Analysis of binding sites on complement factor I that are required for its activity.},
  url          = {http://dx.doi.org/10.1074/jbc.M109.097212},
  volume       = {285},
  year         = {2010},
}