Sandbox Reserved 1121: Difference between revisions
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=== Ca<sup>2+</sup> binding-site === | === Ca<sup>2+</sup> binding-site === | ||
CRP is a calcium dependent structure. In fact, Ca<sup>2+</sup> is required for PC binding, and more precisely for the formation of the PC binding site thanks to structural rearrangements. The protection against denaturation and proteolysis is performed through Ca<sup>2+</sup> binding | CRP is a calcium dependent structure. In fact, Ca<sup>2+</sup> is required for PC binding, and more precisely for the formation of the PC-binding site thanks to structural rearrangements. The protection against denaturation and proteolysis is also performed through Ca<sup>2+</sup>-binding. In the absence of Ca<sup>2+</sup>, hCRP is cleaved between Asn145 and Phe146 by nagarse protease, and between Phe146 and Glu147 by pronase. | ||
Asp60, Asn61, Glu138, Asp140 and the main-chain carbonyl of Gln139 residues allow the first calcium ion binding, and the second is performed through Glu138, Asp140, Glu147 and Gln150 <ref name="ramadan">PMID: 12037301</ref>. | Asp60, Asn61, Glu138, Asp140 and the main-chain carbonyl of Gln139 residues allow the first calcium ion binding, and the second is performed through Glu138, Asp140, Glu147 and Gln150 <ref name="ramadan">PMID: 12037301</ref>. | ||
The two Ca<sup>2+</sup>-binding sites are overlapping in a loop. In the absence of Ca<sup>2+</sup>, the loop changes | The two Ca<sup>2+</sup>-binding sites are overlapping in a loop. In the absence of Ca<sup>2+</sup>, the loop changes conformation and releases the proteolysis site. Therefore Ca<sup>2+</sup> protects CRP form proteolytic cleavage <ref name="agrawal"/>. | ||
=== PC binding site === | === PC binding site === | ||
PC stands for phosphocholine. It is a phospholipid in cell membranes and a plasma lipoprotein <ref name="thompson"/>. The PC-binding site is a hydrophobic pocket constituted by the residues Leu64, Phe66, Thr76 and the two Ca<sup>2+</sup> <ref name="agrawal"/>. | PC stands for phosphocholine. It is a phospholipid in cell membranes and a plasma lipoprotein <ref name="thompson"/>. The PC-binding site is a hydrophobic pocket constituted by the residues Leu64, Phe66, Thr76 and the two Ca<sup>2+</sup> <ref name="agrawal"/>. | ||
The choline function of PC interacts with the two key residues | The choline function of PC interacts with the two key residues Phe66 and Glu81, therefore PC lies inside the PC-binding site <ref name="kumar"/> <ref name="agrawal"/>. | ||
The PC-binding site is next to the Ca<sup>2+</sup>-binding sites on the same face of the CRP protein. The phosphate groupe of PC interacts by coordination with the two Ca<sup>2+</sup> <ref name="agrawal"/>. | The PC-binding site is next to the Ca<sup>2+</sup>-binding sites on the same face of the CRP protein. The phosphate groupe of PC interacts by coordination with the two Ca<sup>2+</sup> <ref name="agrawal"/>. | ||
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 to the CRP-binding <ref name="duclos"/>. | 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 to the CRP-binding <ref name="duclos"/>. | ||
