title: Probing the Acid-Induced Packing Structure Changes of the Molten Globule Domains of a Protein near Equilibrium Unfolding.
abstract: Using simultaneously scanning small-angle X-ray scattering (SAXS) and UV-vis absorption with integrated online size exclusion chromatography, supplemental with molecular dynamics simulations, we unveil the long-postulated global structure evolution of a model multidomain protein bovine serum albumin (BSA) during acid-induced unfolding. Our results differentiate three global packing structures of the three molten globule domains of BSA, forming three intermediates I1, I2, and E along the unfolding pathway. The I1-I2transition, overlooked in all previous studies, involves mainly coordinated reorientations across interconnected molten globule subdomains, and the transition activates a critical pivot domain opening of the protein for entering into the E form, with an unexpectedly large unfolding free energy change of -9.5 kcal mol-1, extracted based on the observed packing structural changes. The revealed local packing flexibility and rigidity of the molten globule domains in the E form elucidate how collective motions of the molten globule domains profoundly influence the folding-unfolding pathway of a multidomain protein.
authors.affiliation: National Synchrotron Radiation Research Center , Hsinchu 30076, Taiwan.
authors.forename: Yi-Qi
authors.identifier: http://orcid.org/0000-0002-2387-3600
authors.initials: YQ
authors.lastname: Yeh
authors.affiliation: National Synchrotron Radiation Research Center , Hsinchu 30076, Taiwan.
authors.forename: Kuei-Fen
authors.initials: KF
authors.lastname: Liao
authors.affiliation: National Synchrotron Radiation Research Center , Hsinchu 30076, Taiwan.
authors.forename: Orion
authors.initials: O
authors.lastname: Shih
authors.affiliation: National Synchrotron Radiation Research Center , Hsinchu 30076, Taiwan.
authors.forename: Ying-Jen
authors.initials: YJ
authors.lastname: Shiu
authors.affiliation: National Synchrotron Radiation Research Center , Hsinchu 30076, Taiwan.
authors.forename: Wei-Ru
authors.initials: WR
authors.lastname: Wu
authors.affiliation: National Synchrotron Radiation Research Center , Hsinchu 30076, Taiwan.
authors.forename: Chun-Jen
authors.initials: CJ
authors.lastname: Su
authors.affiliation: National Synchrotron Radiation Research Center , Hsinchu 30076, Taiwan.
authors.forename: Po-Chang
authors.initials: PC
authors.lastname: Lin
authors.affiliation: National Synchrotron Radiation Research Center , Hsinchu 30076, Taiwan.|Department of Chemical Engineering, National Tsing Hua University , Hsinchu 30013, Taiwan.
authors.forename: U-Ser
authors.initials: US
authors.lastname: Jeng
mesh_terms: D056004:Molecular Dynamics Simulation; D019906:Nuclear Magnetic Resonance, Biomolecular; D011489:Protein Denaturation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D058767:Protein Unfolding; D011506:Proteins / Q000737:chemistry*; D053838:Scattering, Small Angle; D012710:Serum Albumin, Bovine / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D011506:Proteins; D012710:Serum Albumin, Bovine