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This Sandbox is Reserved from 06/12/2018, through 30/06/2019 for use in the course "Structural Biology" taught by Bruno Kieffer at the University of Strasbourg, ESBS. This reservation includes Sandbox Reserved 1480 through Sandbox Reserved 1543.

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Contents 1 Human C-reactive protein (CRP) 1.1 Structure of CRP 1.2 The Calcium and Phosphocholine binding sites 1.3 Interaction with C1q 1.4 Interaction with Fcγ receptors

Human C-reactive protein (CRP)

The C-reactive protein (CRP) is a plasma protein, mainly synthesized by the liver. Its concentration may increase rapidly, as much as 1000-fold or more, in response to tissue injury, infection and inflammation: It's an acute-phase protein.

CRP binds to phosphocholine which is exposed on died or dying cells and expressed on the surfaces of pathogens. Then, it may activate the complement system via interaction with C1q, and enhance phagocytosis by macrophages via its binding to Fcγ receptors. In addition to the fact that this protein has been highly conserved during evolution, this suggests that CRP is a very important part of the innate immune response, in the host defense.

CRP belong to the pentraxin family.

Structure of CRP

CRP is a pentamer: it contains five identical 23-kDa protomers, noncovalently associated (van der Waals contacts or hydrogen bonding) around a central pore. All members of the “pentraxins” family have this general structure.

Each protomer has a recognition face (also called face B) with a phosphocholine binding site (carrying two calcium ions), made of a two-layered β sheet. The other face - the effector face (or face A) - where complement C1q and Fc receptors bind, contain a single α helix. Consequently, the pentamer consist of five α helices on one side, and ten calcium ions on the other.Image:CRP

The Calcium and Phosphocholine binding sites

Interaction with C1q

Interaction with Fcγ receptors