Multiple ligand binding sites on domain seven of human complement factor H
E Giannakis1, D A Male, R J Ormsby
1Department of Microbiology and Infectious Diseases, Flinders Medical Centre, Bedford Park, South Australia 5042.
International Immunopharmacology
|May 23, 2001
Summary
Factor H (fH) regulates the complement system, preventing self-damage. This study reveals a common binding site on fH for heparin, C-reactive protein (CRP), and pathogen M-protein, crucial for immune evasion.
Area of Science:
- Immunology
- Molecular Biology
- Biochemistry
Background:
- The complement system is a key host defense mechanism.
- Factor H (fH) is critical for regulating complement activation on host cells and damaged tissues.
- Pathogens like Group A Streptococcus (GAS) can evade the complement system by binding fH.
Purpose of the Study:
- To investigate the molecular interactions of Factor H (fH) with its ligands.
- To identify the specific region and residues within fH responsible for binding heparin, C-reactive protein (CRP), and pathogen M-protein.
Main Methods:
- Molecular modeling of fH short consensus repeat 7 (SCR 7).
- Alanine replacement mutagenesis to probe functional residues.
- Analysis of fH interactions with heparin, CRP, and M-protein.
Main Results:
- Molecular modeling identified a cluster of positively charged residues on fH SCR 7.
- Mutagenesis confirmed these residues are essential for binding heparin, CRP, and M-protein.
- These findings indicate a shared binding site within fH SCR 7 for multiple ligands.
Conclusions:
- Factor H (fH) utilizes a common site within its SCR 7 domain for interacting with diverse ligands.
- This conserved binding site is crucial for fH's regulatory functions and pathogen immune evasion strategies.
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