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Related Concept Videos

The Equilibrium Binding Constant and Binding Strength02:18

The Equilibrium Binding Constant and Binding Strength

The equilibrium binding constant (Kb) quantifies the strength of a protein-ligand interaction. Kb can be calculated as follows when the reaction is at equilibrium:
The Equilibrium Binding Constant and Binding Strength02:18

The Equilibrium Binding Constant and Binding Strength

The equilibrium binding constant (Kb) quantifies the strength of a protein-ligand interaction. Kb can be calculated as follows when the reaction is at equilibrium:
Complexation Equilibria: Overview01:23

Complexation Equilibria: Overview

Complexation reactions take place when dative or coordinate covalent bonds form between metal ions and ligands. The compounds formed in these reactions are called coordination compounds. The number of bonds formed between the metal ion and the ligands is called its coordination number. Generally, most metal ions in an aqueous solution are solvated by water molecules and thus exist as aqua complexes.
The equilibrium constant of the complexation reaction is represented as the formation constant...
Ligand Binding Sites02:40

Ligand Binding Sites

Proteins are dynamic macromolecules that carry out a wide variety of essential processes; however, the activities of most proteins depend on their interactions with other molecules or ions, known as ligands.
Protein-ligand interactions are quite specific; even though numerous potential ligands surround a cellular protein at any given time, only a particular ligand can bind to that protein. Moreover, a ligand binds only to a dedicated area on the surface of the protein, known as the...
Complexation Equilibria: The Chelate Effect01:19

Complexation Equilibria: The Chelate Effect

In complexation reactions, metal atoms or cations interact with ligands to form donor-acceptor adducts called metal complexes. Ligands that bind through one donor site are monodentate, ligands with two donor sites are bidentate, and those with more than two donor sites are polydentate ligands. For example, ethylene diamine is a bidentate ligand that binds through two nitrogen donor atoms, forming a five-membered ring. EDTA is a polydentate ligand that binds through four oxygen and two nitrogen...
Noncovalent Attractions in Biomolecules02:35

Noncovalent Attractions in Biomolecules

Noncovalent attractions are associations within and between molecules that influence the shape and structural stability of complexes. These interactions differ from covalent bonding in that they do not involve sharing of electrons.
Four types of noncovalent interactions are hydrogen bonds, van der Waals forces, ionic bonds, and hydrophobic interactions.
Hydrogen bonding results from the electrostatic attraction of a hydrogen atom covalently bonded to a strong-electronegative atom like oxygen,...

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Analysis of Protein Complex Formation at Micromolar Concentrations by Coupling Microfluidics with Mass Photometry
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Complement factor H-ligand interactions: self-association, multivalency and dissociation constants.

Stephen J Perkins1, Ruodan Nan, Keying Li

  • 1Department of Structural and Molecular Biology, Darwin Building, University College London, Gower Street, London, UK. s.perkins@ucl.ac.uk

Immunobiology
|December 6, 2011
PubMed
Summary
This summary is machine-generated.

Factor H (FH) regulates complement C3b. This study surveys FH-ligand interactions, revealing FH self-association and weak affinities for C3b and heparin, impacting complement regulation and host cell interactions. Zinc inhibits FH, potentially linking to AMD.

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Area of Science:

  • Immunology
  • Complement System Biology
  • Protein-Ligand Interactions

Background:

  • Factor H (FH) is a key regulator of the complement system's alternative pathway, controlling C3b activity.
  • Understanding FH's interactions with its ligands is crucial but complicated by weak affinities and FH's multivalency.
  • Existing data on FH-ligand binding affinities and physiological relevance require critical review and synthesis.

Purpose of the Study:

  • To conduct the first comprehensive survey of dissociation constants (K(D)) for major FH-ligand interactions.
  • To critically evaluate the physiological significance of these FH-ligand binding characteristics.
  • To explore the implications of FH interactions in conditions like age-related macular degeneration (AMD).

Main Methods:

  • Systematic review and analysis of existing experimental data on FH-ligand interactions.
  • Compilation and comparison of reported dissociation constants (K(D)) for FH with C3b, heparin, C-reactive protein (CRP), and zinc.
  • Modeling of FH-ligand complex formation based on affinity data and FH multivalency.

Main Results:

  • Factor H exhibits significant self-association (5-14% in physiological conditions).
  • FH-C3b and FH-heparin complexes display low micromolar affinities, indicating incomplete formation in vivo.
  • FH-CRP interaction is conditional on elevated CRP levels (acute-phase) and shows allotype-specific binding, while zinc strongly inhibits FH by causing aggregation.

Conclusions:

  • FH self-association influences laboratory assays and physiological functions.
  • Weak affinities of FH for C3b and heparin suggest dynamic interactions and support models of FH binding to cell surfaces and C3b.
  • Zinc-induced FH aggregation and altered FH-CRP binding provide potential mechanisms linking FH dysfunction to AMD pathogenesis.