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Related Concept Videos

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...
Immunoglobulin-like Cell Adhesion Molecules01:31

Immunoglobulin-like Cell Adhesion Molecules

Immunoglobulin-like cell adhesion molecules or Ig-CAMs are a versatile group of cell surface glycoproteins belonging to the immunoglobulin protein superfamily. Ig-CAMs possess the characteristic immunoglobulin protein domains and other domains such as the fibronectin type III domain. The Ig domains are glycosylated to varying degrees in different Ig-CAMs.
Ig-CAMs exhibit either homophilic binding (to other Ig-CAMs) or heterophilic binding (to other ligands such as integrins). While most Ig-CAMs...
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CRISPR and crRNAs

Bacteria and archaea are susceptible to viral infections just like eukaryotes; therefore, they have developed a unique adaptive immune system to protect themselves. Clustered regularly interspaced short palindromic repeats and CRISPR-associated proteins (CRISPR-Cas) are present in more than 45% of known bacteria and 90% of known archaea.
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Bacterial Signaling01:30

Bacterial Signaling

Bacterial signaling can occur within bacteria (intracellular) or between bacteria (intercellular). At times, a group of bacteria behaves like a community. To achieve this, they engage in quorum sensing, the perception of higher cell density that causes changes in gene expression. Quorum sensing involves both extracellular and intracellular signaling. The signaling cascade starts with a molecule called an autoinducer (AI). Individual bacteria produce AIs that move out of the bacterial cell...
IP3/DAG Signaling Pathway01:11

IP3/DAG Signaling Pathway

Membrane lipids such as phosphatidylinositol (PI) are precursors for several membrane-bound and soluble second messengers. Specific kinases phosphorylate PI and produce phosphorylated inositol phospholipids. One such inositol phospholipids are the  phosphatidylinositol-4,5 bisphosphate [PI(4,5)P2], present in the inner half of the lipid bilayer. Upon ligand binding, GPCR stimulates Gq proteins to turn on phospholipase Cꞵ. Activated phospholipase Cꞵ cleaves PI(4,5)P2 and produces two-second...
Protein Complexes with Interchangeable Parts01:57

Protein Complexes with Interchangeable Parts

Groups of proteins may form a complex where each protein in this complex has a different role in the overall execution of the complex’s function. Often some of the proteins in the complex can be replaced by a closely related variant to give a complex that contains many of the same components yet is functionally distinct.
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Related Experiment Video

Updated: Jul 14, 2026

Evaluation of the Interplay Between the Complement Protein C1q and Hyaluronic Acid in Promoting Cell Adhesion
06:54

Evaluation of the Interplay Between the Complement Protein C1q and Hyaluronic Acid in Promoting Cell Adhesion

Published on: June 15, 2019

C1q and its growing family.

Rohit Ghai1, Patrick Waters, Lubka T Roumenina

  • 1Institute of Medical Microbiology, Justus-Liebig-University, Frankfurter Strasse 107, 35392 Giessen, Germany.

Immunobiology
|June 5, 2007
PubMed
Summary

The globular C1q (gC1q) domain acts as a versatile scaffold, linking innate and acquired immunity by recognizing diverse ligands. Its structural similarity to TNF superfamily proteins highlights its broad functional importance.

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Last Updated: Jul 14, 2026

Evaluation of the Interplay Between the Complement Protein C1q and Hyaluronic Acid in Promoting Cell Adhesion
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Area of Science:

  • Immunology
  • Structural Biology
  • Biochemistry

Background:

  • C1q is the classical complement pathway's recognition protein, bridging innate and acquired immunity.
  • The globular domain (gC1q) of C1q recognizes various self and non-self ligands, initiating the classical pathway.
  • The gC1q domain is found in other proteins, forming the C1q family within the larger C1q and TNF superfamily.

Purpose of the Study:

  • To provide an updated review of the structural and functional characteristics of the human C1q gC1q domain.
  • To highlight the significance of the gC1q domain as a versatile structural scaffold.
  • To discuss the diverse functions supported by the gC1q domain across different proteins.

Main Methods:

  • Review of existing literature on C1q and related proteins.
  • Analysis of X-ray crystal structures of gC1q domains.
  • Comparative structural analysis with the TNF ligand family.

Main Results:

  • The gC1q domain adopts a jelly-roll beta-sandwich fold, similar to TNF superfamily members.
  • This domain's structure enables recognition of a wide array of ligands.
  • The gC1q domain serves as a conserved and adaptable scaffold for various biological functions.

Conclusions:

  • The gC1q domain is crucial for C1q's role in immunity and serves as a versatile structural motif in other proteins.
  • Understanding the gC1q domain's structure-function relationship is key to appreciating its broad biological relevance.
  • The C1q and TNF superfamily represents a significant group of proteins with diverse functions mediated by the gC1q domain.