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Riley PW , Cheng H , Samuel D , Roder H , Walsh PN
Dimer dissociation and unfolding mechanism of coagulation factor XI apple 4 domain: Spectroscopic and mutational analysis
Journal of Molecular Biology. 2007 Mar;367(2) :558-573
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The blood coagulation protein factor XI (FXI) consists of a pair of disulfide-linked chains each containing four apple domains and a catalytic domain. The apple 4 domain (A4; F272-E362) mediates non-covalent homodimer formation even when the cysteine involved in an intersubunit disulfide is mutated to serine (C321S). To understand the role of non-covalent interactions stabilizing the FXI dimer, equilibrium unfolding of wild-type A4 and its C321S variant was monitored by circular dichroism, intrinsic tyrosine fluorescence and dynamic light scattering measurements as a function of guanidine hydrochloride concentration. Global analysis of the unimolecular unfolding transition of wild-type A4 revealed a partially unfolded equilibrium intermediate at low to moderate denaturant concentrations. The optically detected equilibrium of C321S A4 also fits best to a three-state model in which the native dimer unfolds via a monomeric intermediate state. Dimer dissociation is characteri!
ISI Document Delivery No.: 146TX Riley, Paul W. Cheng, Hong Samuel, Dharmaraj Roder, Heinrich Walsh, Peter N.