title: Pressure-induced conformational switch of an interfacial protein.
abstract: A special class of proteins adopts an inactive conformation in aqueous solution and activates at an interface (such as the surface of lipid droplet) by switching their conformations. Lipase, an essential enzyme for breaking down lipids, serves as a model system for studying such interfacial proteins. The underlying conformational switch of lipase induced by solvent condition is achieved through changing the status of the gated substrate-access channel. Interestingly, a lipase was also reported to exhibit pressure activation, which indicates it is drastically active at high hydrostatic pressure. To unravel the molecular mechanism of this unusual phenomenon, we examined the structural changes induced by high hydrostatic pressures (up to 1500 MPa) using molecular dynamics simulations. By monitoring the width of the access channel, we found that the protein undergoes a conformational transition and opens the access channel at high pressures (>100 MPa). Particularly, a disordered amphiphilic α5 region of the protein becomes ordered at high pressure. This positive correlation between the channel opening and α5 ordering is consistent with the early findings of the gating motion in the presence of a water-oil interface. Statistical analysis of the ensemble of conformations also reveals the essential collective motions of the protein and how these motions contribute to gating. Arguments are presented as to why heightened sensitivity to high-pressure perturbation can be a general feature of switchable interfacial proteins. Further mutations are also suggested to validate our observations. Proteins 2016; 84:820-827. © 2016 Wiley Periodicals, Inc.
authors.affiliation: UT-ORNL Graduate School of Genome Science and Technology, University of Tennessee, Knoxville, Tennessee, 37996.|Oak Ridge National Laboratory, Center for Molecular Biophysics, Oak Ridge, Tennessee, 37830.
authors.forename: Quentin R
authors.initials: QR
authors.lastname: Johnson
authors.affiliation: Oak Ridge National Laboratory, Center for Molecular Biophysics, Oak Ridge, Tennessee, 37830.|Department of Biochemistry and Cellular & Molecular Biology, University of Tennessee, Knoxville, Tennessee, 37996.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Lindsay
authors.affiliation: Institute of Chemistry, University of the Philippines Diliman, Quezon City, Philippines.
authors.forename: Ricky B
authors.initials: RB
authors.lastname: Nellas
authors.affiliation: Oak Ridge National Laboratory, Center for Molecular Biophysics, Oak Ridge, Tennessee, 37830.|Department of Biochemistry and Cellular & Molecular Biology, University of Tennessee, Knoxville, Tennessee, 37996.
authors.forename: Tongye
authors.initials: T
authors.lastname: Shen
mesh_terms: D006874:Hydrostatic Pressure; D008049:Lipase / Q000737:chemistry*; D056004:Molecular Dynamics Simulation; D011487:Protein Conformation; D011550:Pseudomonas aeruginosa / Q000737:chemistry / Q000201:enzymology*
chemical_list: D008049:Lipase
keywords: barophilic enzyme; gating motion; interfacial protein; molecular dynamics simulation; pressure activation