title: Protein denaturation at a single-molecule level: the effect of nonpolar environments and its implications on the unfolding mechanism by proteases.
abstract: Most proteins are typically folded into predetermined three-dimensional structures in the aqueous cellular environment. However, proteins can be exposed to a nonpolar environment under certain conditions, such as inside the central cavity of chaperones and unfoldases during protein degradation. It remains unclear how folded proteins behave when moved from an aqueous solvent to a nonpolar one. Here, we employed single-molecule atomic force microscopy and molecular dynamics (MD) simulations to investigate the structural and mechanical variations of a polyprotein, I278, during the change from a polar to a nonpolar environment. We found that the polyprotein was unfolded into an unstructured polypeptide spontaneously when pulled into nonpolar solvents. This finding was corroborated by MD simulations where I27 was dragged from water into a nonpolar solvent, revealing details of the unfolding process at the water/nonpolar solvent interface. These results highlight the importance of water in maintaining folding stability, and provide insights into the response of folded proteins to local hydrophobic environments.
authors.affiliation: Key Lab of Advanced Technologies of Materials, Ministry of Education of China, Southwest Jiaotong University, Chengdu 610031, China. cuishuxun@swjtu.edu.cn.
authors.forename: Bo
authors.initials: B
authors.lastname: Cheng
authors.forename: Shaogui
authors.initials: S
authors.lastname: Wu
authors.forename: Shixin
authors.initials: S
authors.lastname: Liu
authors.forename: Piere
authors.initials: P
authors.lastname: Rodriguez-Aliaga
authors.forename: Jin
authors.initials: J
authors.lastname: Yu
authors.forename: Shuxun
authors.initials: S
authors.lastname: Cui
mesh_terms: D002021:Buffers; D003198:Computer Simulation; D064211:Connectin / Q000737:chemistry*; D006801:Humans; D006860:Hydrogen Bonding; D057927:Hydrophobic and Hydrophilic Interactions; D018625:Microscopy, Atomic Force; D008958:Models, Molecular; D018832:Molecular Chaperones / Q000737:chemistry; D056004:Molecular Dynamics Simulation; D010447:Peptide Hydrolases / Q000737:chemistry*; D010455:Peptides / Q000737:chemistry; D020815:Polyproteins / Q000737:chemistry*; D011489:Protein Denaturation; D017510:Protein Folding; D058767:Protein Unfolding; D012997:Solvents / Q000737:chemistry; D013314:Stress, Mechanical; D014867:Water / Q000737:chemistry
chemical_list: D002021:Buffers; D064211:Connectin; D018832:Molecular Chaperones; D010455:Peptides; D020815:Polyproteins; D012997:Solvents; C577285:TTN protein, human; D014867:Water; D010447:Peptide Hydrolases