A dry molten globule-like intermediate during the base-induced unfolding of a multidomain protein

The nature of the initial structural events during the base-induced unfolding of the native (N) state of proteins is poorly understood. Combining site-specific fluorescence resonance energy transfer, size exclusion chromatography, dynamic fluorescence quenching, red-edge excitation shift and circula...

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Bibliographic Details
Published in:Physical chemistry chemical physics : PCCP 2017-11, Vol.19 (44), p.30207-30216
Main Authors: Acharya, Nirbhik, Mishra, Prajna, Jha, Santosh Kumar
Format: Article
Language:English
Subjects:
Dichroism
Disruption
Fluorescence
Free energy
Helices
Loosening
Proteins
Size exclusion chromatography
Solvation
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Summary:The nature of the initial structural events during the base-induced unfolding of the native (N) state of proteins is poorly understood. Combining site-specific fluorescence resonance energy transfer, size exclusion chromatography, dynamic fluorescence quenching, red-edge excitation shift and circular dichroism spectroscopy, we show here that an early intermediate during the base-induced unfolding of a multidomain protein, i.e., the B form, has features of a dry molten globule. We show that the N ⇌ B transition involves protein expansion and loosening of packing of inter-domain helices near domains I and II without the disruption of intra-domain packing or any change in hydration of the inter-domain region which resembles a molten hydrocarbon. Surprisingly, the disruption of inter-domain packing accounts for 40-45% of the total change in free energy of complete unfolding. Our results show that the disruption of van der Waals packing can be decoupled in different regions of a protein and could occur prior to hydrophobic solvation during base-induced unfolding, challenging the existing notion.
ISSN:1463-9076
1463-9084
DOI:10.1039/c7cp06614g