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Classical antibody-mediated complement activation

Summary

Organism

Homo sapiens (human)

Reactome

R-HSA-173623

PubChem

R-HSA-173623

Description

C1, the first component of complement is a complex containing three protein species, C1q, C1r, and C1s. C1q is assembled from six identical subunits each of which consists of three homologous chains (A, B, and C). These chains form a globular domain at the C-terminus, followed by the "neck" and a coil in the "stalk." The six subunits are held together by the collagenous stalk parts (giving rise to the comparison of C1q with a "bunch of six tulips"). The stalks also interact with the [C1s:C1r:C1r:C1s] tetramer assembled in a linear chain. Binding of an antigen to an antibody of the IgM or IgG class induces a conformational change in the Fc domain of the antibody that allows it to bind to the C1q component of C1. C1 activation requires interaction with two separate Fc domains, so pentavalent IgM antibody is far more efficient at complement activation than IgG antibody. Antibody binding results in a conformational change in the C1r component of the C1 complex and a proteolytic cleavage of C1r, activating it. Active C1r then cleaves and activates the C1s component of the C1 complex (Muller-Eberhard 1988).

Click on a node on the pathway to see its details. Glycoproteins are marked with a glycoprotein icon in their name.

SPV: a JavaScript Signaling Pathway Visualizer, Bioinformatics, 2018

Displaying entries **1 - 10** of 16 in total

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UniProt ID	Protein Name	Gene Symbol	Pathway Viewer
P00736	Complement C1r subcomponent	C1R	view
P01593	Immunoglobulin kappa variable 1D-33	IGKV1D-33	view
P01705	Immunoglobulin lambda variable 2-23	IGLV2-23	view
P01824	Immunoglobulin heavy variable 4-39	IGHV4-39	view
P01834	Immunoglobulin kappa constant	IGKC	view
P01857	Immunoglobulin heavy constant gamma 1	IGHG1	view
P01859	Immunoglobulin heavy constant gamma 2	IGHG2	view
P01860	Immunoglobulin heavy constant gamma 3	IGHG3	view
P01861	Immunoglobulin heavy constant gamma 4	IGHG4	view
P02745	Complement C1q subcomponent subunit A	C1QA	view

Displaying 1 entry
GlyCosmos Lectin	UniProt ID	Lectin Name	Pathway Viewer
GL_002302	P02741	C-reactive protein	view

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