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Updated: Sep 16, 2025

X-Ray Crystallography to Study the Oligomeric State Transition of the Thermotoga maritima M42 Aminopeptidase TmPep1050
Published on: May 13, 2020
The sheet-to-helix transition is a potential gas-phase unfolding pathway for a multidomain protein CRM197
Xia Xu1, Guiqian Yang2, Zhen Zheng3
1Tianjin Key Laboratory of Biosensing and Molecular Recognition, Research Center for Analytical Science, Frontiers Science Center for New Organic Matter, College of Chemistry, Nankai University, Tianjin 300071, China.
Abstract:
Despite the expansive applications of gas-phase unfolding techniques, the molecular mechanism for the solvent-free forced unfolding pathway which substrate multidomain proteins usually adopt remains elusive at the secondary structure level. Herein, upon carefully selecting CRM197 as a therapeutically-relevant model system containing multiple secondary structure-separated domains, we systematically examine its solvent-free unfolding pathway. Further-more, utilizing the hybrid of noncovalent chemical probing with niacinamide and ion mobility-mass spectrometry-guided all-atom molecular dynamics simulations, we map a nearly complete unfolding atlas for the conjugate vaccine carrier protein CRM197 in a domain- and secondary structure-resolved manner. The totality of our data supports the preferential unfolding of the sheet-rich domain, indicating the dynamic transition from β-sheet to α-helices, and demonstrating that helices exhibit comparatively higher stability than β-sheets. We propose that this sheet-to-helix dynamic transition may be central to the gas-phase unfolding pathways of multidomain proteins, suggesting the need for systematic studies on additional multidomain protein systems.
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