Article

Structural basis of ligand specificity in the human pentraxins, C-reactive protein and serum amyloid P component

Laboratory of Protein Crystallography, Acute Phase Proteins, Division of Medicine, Royal Free Campus, University College London Medical School, Rowland Hill Street, London NW3 2PF, UK.
Journal of Molecular Recognition (Impact Factor: 2.15). 03/2011; 24(2):371-7. DOI: 10.1002/jmr.1090
Source: PubMed

ABSTRACT

The normal physiological roles of the phylogenetically conserved human plasma proteins C-reactive protein (CRP) and serum amyloid P component (SAP) are not known. Novel drugs targeting their ligand specificities are in clinical development as both proteins have significant pathophysiological effects, SAP in promoting amyloidosis and CRP in exacerbating ischemic injury. Both proteins bind to phosphoethanolamine and we show here that, under physiological conditions, phosphoethanolamine is bound with higher affinity by human SAP than by human CRP. An explanation is provided by X-ray crystal structures that show SAP residue Tyr74 allowing additional hydrophobic protein-ligand interactions compared with the equivalent Thr76 of CRP. Docking simulations show many more low energy positions for phosphoethanolamine bound by CRP than by SAP and are consistent with the crystallographic and functional binding results. These fundamental observations on structure-activity relationships will aid the design of improved pentraxin targeting drugs.

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Available from: Halina Mikolajek
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    • "In addition, common turbidimetry is not sensitive enough to meet the required sensitivity for hsCRP measurements. The assay conditions of the functional nephelometric CRP assay correspond with a final phosphocholine concentration in the cuvette of about 8 µmol/L, which is about four times the Kd value of CRP for phosphocholine[26]. In this way, impact of light scattering of the Intralipid ® particles on the dynamic range of the test was kept to a minimum ( ± 1100 bits, which accounts for ± 10% of the total dynamic range of the detection system), while still keeping a comfortable phosphocholine binding capacity . "
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    ABSTRACT: The measurement of C-reactive protein (CRP) concentrations has been of interest as a classical marker of acute phase response; in addition, it has been of particular interest in cardiovascular risk stratification where high-sensitive measurements are necessary. Since CRP is able to bind phospholipids (mainly phosphocholine) in the presence of calcium ions, we explored the possibilities of developing a high-sensitive affordable nephelometric CRP assay based on diluted soy oil emulsions. Methods: Serum (or heparinized plasma) was mixed with Intralipid 20% in Tris-calcium buffer (pH 7.5). After 12 min of incubation at 37 degrees C, the CRP-phospholipid complexes were measured by nephelometry (840 nm) using a BN II nephelometer (Siemens). Results (n=97) were compared with those obtained using a typical immunoturbidimetric method (Roche). Results: Imprecision of the functional nephelometric assay was evaluated using three human serum pools. Within-run coefficients of variation (CVs) for level 1, 2 and 3 were 6.1%, 4.7% and 4.5%, respectively, and between-run CVs were 17.6%, 18.8% and 11.3%, respectively. Good agreement was obtained between the functional nephelometric and the immunoturbidimetric CRP assay in a concentration range from 0.1 mg/L to 50 mg/L (r=0.884). A logit-log calibration curve was made between 0.056 mg/L and 1.785 mg/L. The limit of detection was 0.5 mg/L. Conclusions: The functional nephelometric CRP assay allowed high-sensitive CRP determinations in serum and plasma. Since the assay is species independent, the described functional CRP assay could be used for veterinary purposes as well.
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    • "Between the N-terminal 9–10 Calx-beta motifs, there are about 200 amino acids forming a pentraxin (PTX) domain with a distinctive flattened β-jellyroll structure (Fig. 1a, b). Members of pentraxin family include C-reactive protein and Serum amyloid P component, which could mediate acute immunological responses or extracellular proteins-receptor interactions (Lu et al. 2008; Mikolajek et al. 2011). About 2,000 amino acids after the PTX domain, an EAR (epilepsy associated repeats) domain is inserted between 22 and 23 Calx-beta motifs (Fig. 1a, b). "
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    ABSTRACT: The very large G protein coupled receptor (Vlgr1) is a member of adhesion receptors or large N-terminal family B-7 transmembrane helixes (LNB7TM) receptors within the seven trans-membrane receptor superfamily. Vlgr1 is the largest GPCR identified to date; its mRNA spans 19 kb and encodes 6,300 amino acids. Vlgr1 is a core component of ankle-link complex in inner ear hair cells. Knock-out and mutation mouse models show that loss of Vlgr1 function leads to abnormal stereociliary development and hearing loss, indicating crucial roles of Vlgr1 in hearing transduction or auditory system development. Over the past 10 or so years, human genetics data suggested that Vlgr1 mutations cause Usher syndromes and seizures. Although significant progresses have been made, the details of Vlgr1's function in hair cells, its signaling cascade, and the mechanisms underlying causative effects of Vlgr1 mutations in human diseases remain elusive and ask for further investigation.
    Full-text · Article · Nov 2012 · Journal of Molecular Neuroscience
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    • "The other face, designated B, contains a ligand-binding concave face. The ligand-binding site consists of several residues that form a hydrophobic pocket and two Ca 2+ ions [14] [15]. The contact domain between subunits comprises the open-core end of the two-layered b sheet of one protomer and the N-and C-terminal strands of another [16]. "
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    ABSTRACT: The short pentraxins C-reactive protein (CRP) and serum amyloid P component (SAP) constitute a group of innate immune receptors that trigger immune activation by detecting molecules of the microbial cell wall. Here, we examined the evolution of short pentraxins in Murinae lineages. By molecular evolutionary analysis, CRP and SAP have been experiencing rapid diversification, driven by adaptive selection. Further, our protein modeling demonstrates that adaptively selected amino acids lie in the ligand-binding region and contact region between subunits. Our findings suggest that rapid diversification of these regions could contribute to the determinants of recognizing specificity and the interaction between subunits.
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