Biochemically prepared C-reactive protein conformational states differentially affect C1q binding

• Published in: BBA advances Vol. 2; p. 100058
• Main Authors: Moon, Carrie L., Alnaas, Aml A., Cai, Yuheng, Reed, Scott M., Knowles, Michelle K.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01-01-2022; Elsevier
• Subjects: ANS; Circular dichroism; Complement immune response; Dynamic light scattering; ELISA; mCRP; Non-denaturing PAGE; pCRP; Tryptophan fluorescence; GndHCl; CRP; pCRP; Non-denaturing PAGE; Dynamic light scattering; Complement immune response; mCRP; ANS; Tryptophan fluorescence; ELISA; Circular dichroism
• ISSN: 2667-1603; 2667-1603
• DOI: 10.1016/j.bbadva.2022.100058

•The pCRP to mCRP change is measured using several methods sensitive to conformation.•Several chemical treatments yield modified CRP, few lead to a form that binds C1q.•Modified CRP binding to C1q is achieved with dilute SDS and heat treatment.
C-reactive protein (CRP) is commonly measured as an inflammatory marker in patient studies for coronary heart disease, autoimmune disease and recent acute infections. Due to a correlation of CRP to a vast number of disease states, CRP is a well-studied protein in medical literature with over 16000 references in PubMed [1]. However, the biochemical and structural variations of CRP are not well understood in regards to their binding of complement immune response proteins. Conformations of CRP are thought to affect disease states differently, with a modified form showing neoepitopes and activating the complement immune response through C1q binding. In this work, we compare the unfolding of CRP using chemical denaturants and identify which states of CRP bind a downstream complement immune response binding partner (C1q). We used guanidine HCl (GndHCl), urea/EDTA, and 0.01% SDS with heat to perturb the pentameric state. All treatments give rise to a monomeric state in non-denaturing polyacrylamide gel electrophoresis experiments, but only treatment with certain concentrations of denaturant or dilute SDS with heat maintains CRP function with a key downstream binding partner, C1q, as measured by enzyme-linked immunosorbent assays. The results suggest that the final form of modified CRP and its ability to mimic biological binding is dependent on the preparation method.
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