Sandbox Reserved 1121: Difference between revisions

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Tertiary and quaternary structure:

The structure of CRP has been determined by X-ray crystallograph at 3 Å resolution. Like SAP, the protein consists of five protomers, uncovalently bonded and nonglycosylated that are arranged symmetrically around a central pore <ref name="Volanakis">PMID: 11532280</ref>.

The structure of CRP has been determined by X-ray crystallograph at 3 Å resolution. Like SAP, the protein consists of five protomers, uncovalently bonded and nonglycosylated that are arranged symmetrically around a central pore <ref name="Volanakis">PMID: 11532280</ref> <ref name="duclos"/>.

The diameter of the CRP pentamer is 102 Å, the inner pore diameter is 30 Å and the diameter of a subunit is 36 Å <ref name="agrawal">PMID: 19799114 </ref>.

Thereafter, the ligand-binding face of the molecule will be called B and the opposite face will be called A. The B face binds two Ca2+ ions and a phosphocholine per subunit. The A face, recognizable by the presence of ~~the~~ α-helix, can interact with C1q and Fc receptors <ref name="duclos">PMID: 15531769 </ref>.

Thereafter, the ligand-binding face of the molecule will be called B and the opposite face will be called A. The B face binds two Ca2+ ions and a phosphocholine per subunit. The A face, recognizable by the presence of an α-helix and a deep cavity, can interact with C1q and Fc receptors <ref name="duclos">PMID: 15531769 </ref>.

=== Ca2+ binding-site ===

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PC stands for phosphocholine. It is a phospholipid in cell membranes and a plasma lipoproteins <ref name="thompson"/>. Phe-66 and Glu-81 are the two key residues that enable the binding of PC <ref name="kumar"/>. They interact with the choline function of PC, which therefore lies inside the PC-binding site.

CRP binds the phosphocholine and other ligands in a Ca2+-dependent way. The PC-binding site is next to the Ca2+-binding sites on the same face of the CRP protein. The PC-binding site is a hydrophobic pocket constituted by the residues Leu64, Phe66, Thr76 and the two Ca2+. The phosphate groupe of PC interacts by coordination with the two Ca2+.

The affinity of CRP for PC increases with the concentration of PC. A surface containing a high density of PC, such as C-polycaccharide, is therefore propitious for the CRP-binding <ref name="duclos"/>.

CRP can also bind chromatin, histones, small nuclear robonucleoproteins nuclear envelop proteins and nucleosomes Ca2+-dependently <ref name="agrawal"/>.

[[Image:Phosphocholine.PNG | thumb | Phosphocholine-binding site <ref>The PyMOL Molecular Graphics System, Version 1.8 Schrödinger, LLC.</ref>]]

[[Image:Phosphocholine.PNG | thumb | Phosphocholine and Ca2+-binding site <ref>The PyMOL Molecular Graphics System, Version 1.8 Schrödinger, LLC.</ref>]]

== Function ==

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@@ Line 17: / Line 17: @@
 Tertiary and quaternary structure:
-The structure of CRP has been determined by X-ray crystallograph at 3 Å resolution. Like SAP, the protein consists of five protomers, uncovalently bonded and nonglycosylated that are arranged symmetrically around a central pore <ref name="Volanakis">PMID: 11532280</ref>.
+The structure of CRP has been determined by X-ray crystallograph at 3 Å resolution. Like SAP, the protein consists of five protomers, uncovalently bonded and nonglycosylated that are arranged symmetrically around a central pore <ref name="Volanakis">PMID: 11532280</ref> <ref name="duclos"/>.
 The diameter of the CRP pentamer is 102 Å, the inner pore diameter is 30 Å and the diameter of a subunit is 36 Å <ref name="agrawal">PMID: 19799114 </ref>.
-Thereafter, the ligand-binding face of the molecule will be called B and the opposite face will be called A. The B face binds two Ca<sup>2+</sup> ions and a phosphocholine per subunit. The A face, recognizable by the presence of the α-helix, can interact with C1q and Fc receptors <ref name="duclos">PMID: 15531769 </ref>.
+Thereafter, the ligand-binding face of the molecule will be called B and the opposite face will be called A. The B face binds two Ca<sup>2+</sup> ions and a phosphocholine per subunit. The A face, recognizable by the presence of an α-helix and a deep cavity, can interact with C1q and Fc receptors <ref name="duclos">PMID: 15531769 </ref>.
 === Ca<sup>2+</sup> binding-site ===
@@ Line 29: / Line 29: @@
 PC stands for phosphocholine. It is a phospholipid in cell membranes and a plasma lipoproteins <ref name="thompson"/>. Phe-66 and Glu-81 are the two key residues that enable the binding of PC <ref name="kumar"/>. They interact with the choline function of PC, which therefore lies inside the PC-binding site.
 CRP binds the phosphocholine and other ligands in a Ca<sup>2+</sup>-dependent way. The PC-binding site is next to the Ca<sup>2+</sup>-binding sites on the same face of the CRP protein. The PC-binding site is a hydrophobic pocket constituted by the residues Leu64, Phe66, Thr76 and the two Ca<sup>2+</sup>. The phosphate groupe of PC interacts by coordination with the two Ca<sup>2+</sup>.
+The affinity of CRP for PC increases with the concentration of PC. A surface containing  a high density of PC, such as C-polycaccharide, is therefore propitious for the CRP-binding <ref name="duclos"/>.
 CRP can also bind chromatin, histones, small nuclear robonucleoproteins nuclear envelop proteins and nucleosomes Ca<sup>2+</sup>-dependently <ref name="agrawal"/>.
-[[Image:Phosphocholine.PNG | thumb | Phosphocholine-binding site <ref>The PyMOL Molecular Graphics System, Version 1.8 Schrödinger, LLC.</ref>]]
+[[Image:Phosphocholine.PNG | thumb | Phosphocholine and Ca<sup>2+</sup>-binding site <ref>The PyMOL Molecular Graphics System, Version 1.8 Schrödinger, LLC.</ref>]]
 == Function ==