Analysis of binding sites on complement factor I using artificial N-linked glycosylation
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 disulfide bridge; the light chain comprises only the serine protease (SP) domain, whereas the heavy chain contains the FI membrane attack complex domain (FIMAC), CD5 domain, and low density lipoprotein receptor 1 (LDLr1) and LDLr2 domains. To better understand how FI inhibits complement, we used homology-based three-dimensional 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 (K(m)) of all FI mutants toward a small substrate was not increased. We found that many mutations in the FIMAC and SP domains nearly abolished the ability of FI to degrade C4b and C3b in the fluid phase and on the surface, irrespective of the cofactor used. On the other hand, only a 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.
| Medienart: |
E-Artikel |
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| Erscheinungsjahr: |
2012 |
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| Erschienen: |
2012 |
| Enthalten in: |
Zur Gesamtaufnahme - volume:287 |
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| Enthalten in: |
The Journal of biological chemistry - 287(2012), 17 vom: 20. Apr., Seite 13572-83 |
| Sprache: |
Englisch |
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| Beteiligte Personen: |
Sanchez-Gallego, Jose I [VerfasserIn] |
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| Links: |
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| Themen: |
80295-43-8 |
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| Anmerkungen: |
Date Completed 17.07.2012 Date Revised 21.10.2021 published: Print-Electronic Citation Status MEDLINE |
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| doi: |
10.1074/jbc.M111.326298 |
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| funding: |
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| Förderinstitution / Projekttitel: |
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| PPN (Katalog-ID): |
NLM215967224 |
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| 100 | 1 | |a Sanchez-Gallego, Jose I |e verfasserin |4 aut | |
| 245 | 1 | 0 | |a Analysis of binding sites on complement factor I using artificial N-linked glycosylation |
| 264 | 1 | |c 2012 | |
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| 500 | |a Date Completed 17.07.2012 | ||
| 500 | |a Date Revised 21.10.2021 | ||
| 500 | |a published: Print-Electronic | ||
| 500 | |a Citation Status MEDLINE | ||
| 520 | |a 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 disulfide bridge; the light chain comprises only the serine protease (SP) domain, whereas the heavy chain contains the FI membrane attack complex domain (FIMAC), CD5 domain, and low density lipoprotein receptor 1 (LDLr1) and LDLr2 domains. To better understand how FI inhibits complement, we used homology-based three-dimensional 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 (K(m)) of all FI mutants toward a small substrate was not increased. We found that many mutations in the FIMAC and SP domains nearly abolished the ability of FI to degrade C4b and C3b in the fluid phase and on the surface, irrespective of the cofactor used. On the other hand, only a 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 | ||
| 650 | 4 | |a Journal Article | |
| 650 | 4 | |a Research Support, Non-U.S. Gov't | |
| 650 | 7 | |a Recombinant Proteins |2 NLM | |
| 650 | 7 | |a Complement C3b |2 NLM | |
| 650 | 7 | |a 80295-43-8 |2 NLM | |
| 650 | 7 | |a Complement C4b |2 NLM | |
| 650 | 7 | |a 80295-50-7 |2 NLM | |
| 650 | 7 | |a Complement Factor I |2 NLM | |
| 650 | 7 | |a EC 3.4.21.45 |2 NLM | |
| 700 | 1 | |a Groeneveld, Tom W L |e verfasserin |4 aut | |
| 700 | 1 | |a Krentz, Stefanie |e verfasserin |4 aut | |
| 700 | 1 | |a Nilsson, Sara C |e verfasserin |4 aut | |
| 700 | 1 | |a Villoutreix, Bruno O |e verfasserin |4 aut | |
| 700 | 1 | |a Blom, Anna M |e verfasserin |4 aut | |
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| 856 | 4 | 0 | |u http://dx.doi.org/10.1074/jbc.M111.326298 |3 Volltext |
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