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Title: Pathophysiological condition changes the conformation of a flexible FBG-related protein, switching it from pathogen-recognition to host-interaction
Authors: Zhang, J.
Yang, L. 
Anand, G.S. 
Ho, B.
Ding, J.L. 
Keywords: C-reactive protein (CRP)
Conformational change
Fibrinogen-like domain (FBG)
Fibrinogen-related protein (FREP)
Hydrogen-deuterium exchange mass spectrometry (HDMS)
Issue Date: Oct-2011
Citation: Zhang, J., Yang, L., Anand, G.S., Ho, B., Ding, J.L. (2011-10). Pathophysiological condition changes the conformation of a flexible FBG-related protein, switching it from pathogen-recognition to host-interaction. Biochimie 93 (10) : 1710-1719. ScholarBank@NUS Repository.
Abstract: Although homeostatic disturbance of the blood pH and calcium in the vicinity of tissue injury/malignancy/local infection seems subtle, it can cause substantial pathophysiological consequences, a phenomenon which has remained largely unexplored. The fibrinogen-related proteins (FREPs) containing fibrinogen-like domain (FBG) represent a conserved protein family with a common calcium-binding region, implying the presence of elements responsive to physiological perturbation. Here, we studied the molecular interaction between a representative FREP, the M-ficolin, and an acute phase blood protein, the C-reactive protein (CRP), both of which are known to trigger and control seminal pathways in infection and injury. Using hydrogen-deuterium exchange mass spectrometry, we showed that the C-terminal region of M-ficolin FBG underwent dramatic conformational change upon pH and calcium perturbations. Biochemical and biophysical assays showed that under defined pathophysiological condition (pH 6.5, 2.0 mM calcium), the FBG:CRP interaction occurred more strongly compared to that under physiological condition (pH 7.4, 2.5 mM calcium). We identified the binding interface between CRP and FBG, locating it to the pH- and calcium-sensitive C-terminal region of FBG. By site-directed mutagenesis, we determined H284 in the N-acetylglucosamine (GlcNAc)-binding pocket of the FBG, to be the critical CRP-binding residue. This conformational switch involving H284, explains how the pathophysiologically-driven FBG:CRP interaction diverts the M-ficolin away from GlcNAc/pathogen-recognition to host protein-protein interaction, thus enabling the host to regain homeostatic control. Our elucidation of the binding interface at the flexible FBG domain provides insights into the bioactive centre of the M-ficolin, and possibly other FREPs, which might aid future development of immunomodulators. © 2011 Elsevier Masson SAS. All rights reserved.
Source Title: Biochimie
ISSN: 03009084
DOI: 10.1016/j.biochi.2011.06.003
Appears in Collections:Staff Publications

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