Related Experiment Video

Updated: Aug 8, 2026

Membrane-SPINE: A Biochemical Tool to Identify Protein-protein Interactions of Membrane Proteins In Vivo
10:53

Membrane-SPINE: A Biochemical Tool to Identify Protein-protein Interactions of Membrane Proteins In Vivo

Published on: November 7, 2013

Binding of human complement component C4b-binding protein (C4BP) to Streptococcus pyogenes involves the C4b-binding

P Accardo1, P Sánchez-Corral, O Criado

  • 1Department of Immunology, Center for Biological Research, CSIC, Madrid, Spain.

Journal of Immunology (Baltimore, Md. : 1950)
|December 1, 1996
PubMed

Insights

Streptococcus pyogenes evades the immune system by mimicking human complement protein C4b. This molecular mimicry allows bacteria to bind human C4b-binding protein (hC4BP), hindering pathogen elimination.

Area of Science:

  • Immunology
  • Microbiology
  • Molecular Biology

Background:

  • The complement system is crucial for eliminating pathogens via C3b and C4b protein deposition.
  • Pathogens like Streptococcus pyogenes possess mechanisms to evade host complement defenses.

Purpose of the Study:

  • To elucidate the molecular mechanism by which Streptococcus pyogenes interacts with human C4b-binding protein (hC4BP).
  • To understand how this interaction impacts complement deposition on the bacterial surface.

Main Methods:

  • Investigated the binding interaction between streptococcal surface molecules and hC4BP.
  • Characterized the specific binding site on hC4BP involved in the interaction.

Main Results:

  • Streptococcal surface molecules bind to hC4BP at a site identical to the C4b binding site.
  • The interaction involves multiple binding surfaces within the short consensus repeats 1-3 of hC4BP's alpha-chain.

Conclusions:

  • Streptococcus pyogenes employs molecular mimicry, presenting surface structures that resemble human C4b epitopes.
  • This mimicry facilitates binding to hC4BP, potentially downregulating complement-mediated bacterial clearance.

More Related Videos

Monitoring the Assembly of a Secreted Bacterial Virulence Factor Using Site-specific Crosslinking11:33

Monitoring the Assembly of a Secreted Bacterial Virulence Factor Using Site-specific Crosslinking

Published on: December 17, 2013

Cell Surface Receptor Identification Using Genome-Scale CRISPR/Cas9 Genetic Screens08:49

Cell Surface Receptor Identification Using Genome-Scale CRISPR/Cas9 Genetic Screens

Published on: June 6, 2020

Related Concept Videos

Ligand Binding and Linkage00:49

Ligand Binding and Linkage

Allosteric proteins have more than one ligand binding site; the binding of a ligand to any of these sites influences the binding of ligands to the other sites. When a protein is allosteric, its binding sites are called coupled or linked.  In the case of enzymes, the site that binds to the substrate is known as the active site and the other site is known as the regulatory site. When a ligand binds to the regulatory site, this leads to conformational changes in the protein that can influence the...
Antibody Actions01:26

Antibody Actions

Antibodies, or immunoglobulins, are critical players in the immune system's arsenal against invading pathogens. Produced by B cells and plasma cells, their primary role is to detect and bind to specific antigens, molecules found on the surface of pathogens like bacteria or viruses. Beyond antigen recognition, antibodies perform several vital functions that contribute to immune defense.
Neutralization
Antibodies can bind to pathogens, preventing them from infecting host cells. This process...
Complement System01:27

Complement System

The complement system is a group of approximately 20 plasma proteins that strengthen the body's defenses against infections through opsonization, inflammation, and cell lysis. Opsonization involves coating pathogens with complement proteins, making them more recognizable and facilitating phagocyte engulfment. Certain complement proteins induce inflammation that attracts immune cells to the site of infection. Cell lysis involves the destruction of pathogens through the formation of a membrane...
Hypersensitivity Reactions: Cytolytic Reactions01:01

Hypersensitivity Reactions: Cytolytic Reactions

Type II hypersensitivity involves IgG and IgM antibodies targeting cell surface antigens, leading to cell destruction. This can occur through complement activation, antibody-dependent cell-mediated cytotoxicity (ADCC), or acting as opsonins for phagocytosis. When excessive, these reactions cause significant tissue damage.Drug-induced hemolytic anemia is a common example, where drugs like penicillin or cephalosporins bind to red blood cells, forming drug-protein complexes. These complexes...
Determinants of Bacterial Pathogenicity and Virulence01:20

Determinants of Bacterial Pathogenicity and Virulence

Pathogenic bacteria employ a variety of strategies to establish infections, including the secretion of extracellular enzymes that act as potent virulence factors. These enzymes facilitate bacterial colonization of host tissues and help evade immune surveillance. By targeting structural components of host tissues and interfering with immune mechanisms, these enzymes play a pivotal role in disease progression.Extracellular Enzymes Facilitating Tissue Invasion: Several bacterial pathogens secrete...
Streptococcal Pharyngitis01:27

Streptococcal Pharyngitis

Streptococcal pharyngitis, commonly known as “strep throat,” is an acute infection of the oropharyngeal tissues caused by the Gram‑positive Group A Streptococcus (Streptococcus pyogenes). Transmission occurs primarily through respiratory droplets expelled during coughing, sneezing, or talking.Mechanisms of Host Entry and Immune EvasionUpon entering the host, S. pyogenes adheres to the mucosal epithelial cells of the pharynx via surface proteins, notably lipoteichoic acid and the antiphagocytic...