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Issue 21, 2017
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High-affinity recognition of the human C-reactive protein independent of phosphocholine

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Abstract

A high-affinity polypeptide conjugate 4-C25L22-DQ, has been developed for the molecular recognition of the human C-reactive protein, CRP, a well-known inflammation biomarker. CRP is one of the most frequently quantified targets in diagnostic applications and a target in drug development. With the exception of antibodies, most molecular constructs take advantage of the known affinity for CRP of phosphocholine that depends on Ca2+ for its ability to bind. 4-C25L22-DQ which is unrelated to phosphocholine binds in the absence of Ca2+ with a dissociation constant of 760 nM, an order of magnitude lower than that of phosphocholine, the KD of which is 5 μM. The small organic molecule 2-oxo-1,2-dihydroquinoline-8-carboxylic acid (DQ) was designed based on the structural similarities between three hits from a set of compounds selected from a building block collection and evaluated with regards to affinity for CRP by NMR spectroscopy. 4-C25L22-DQ was shown in a competition experiment to bind CRP three orders of magnitude more strongly than DQ itself, and in a pull-down experiment 4-C25L22-DQ was shown to extract CRP from human serum. The development of a robust and phosphocholine-independent recognition element provides unprecedented opportunities in bioanalytical applications in vivo and in vitro under conditions where the concentration of Ca2+ ions is low, or where Ca2+ binding agents such as EDTA or heparin are needed to prevent blood coagulation. The identification from a compound library of a small organic molecule and its conjugation to a small set of polypeptides, none of which were previously known to bind CRP, illustrates a convenient and general route to selective high-affinity binders for proteins with dissociation constants in the μM to nM range for which no small molecule ligands are known.

Graphical abstract: High-affinity recognition of the human C-reactive protein independent of phosphocholine

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Publication details

The article was received on 20 Mar 2017, accepted on 05 May 2017 and first published on 08 May 2017


Article type: Paper
DOI: 10.1039/C7OB00684E
Citation: Org. Biomol. Chem., 2017,15, 4644-4654
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    High-affinity recognition of the human C-reactive protein independent of phosphocholine

    J. Yang, A. Gustavsson, M. Haraldsson, G. Karlsson, T. Norberg and L. Baltzer, Org. Biomol. Chem., 2017, 15, 4644
    DOI: 10.1039/C7OB00684E

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