title: Crystallographic Investigation of Imidazolium Ionic Liquid Effects on Enzyme Structure.
abstract: We present the first crystallographic insight into the interactions of an ionic liquid (IL) with an enzyme, which has widespread implications for stabilizing enzymes in IL media for biocatalysis. Structures of Bacillus subtilis lipase A (lipA) and an IL-stable variant (QM-lipA) were obtained in the presence of increasing concentrations of 1-butyl-3-methylimidazolium chloride ([BMIM][Cl]). These studies revealed that the [BMIM] cation interacts with surface residues through hydrophobic and cation-π interactions. Of specific interest was the disruption of internal stacking interactions of aromatic side chains by [BMIM], which provides structural evidence for the mechanism of enzyme denaturation by ILs. The interaction of [BMIM] and Cl ions with lipA was reduced by the stabilizing mutations Y49E and G158E in QM-lipA. Ultimately, these findings present the molecular basis for stabilizing enzymes from IL-induced inactivation, as well as the selection of ILs that are less denaturing.
authors.affiliation: Department of Chemical and Biological Engineering, University of Colorado, Campus Box 596, Boulder, CO, 80309, USA.
authors.forename: Erik M
authors.initials: EM
authors.lastname: Nordwald
authors.affiliation: Department of Chemical and Biological Engineering, University of Colorado, Campus Box 596, Boulder, CO, 80309, USA.
authors.forename: Joseph G
authors.initials: JG
authors.lastname: Plaks
authors.affiliation: Department of Chemical and Biological Engineering, University of Colorado, Campus Box 596, Boulder, CO, 80309, USA.
authors.forename: Jared R
authors.initials: JR
authors.lastname: Snell
authors.affiliation: Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO, 80309, USA.
authors.forename: Marcelo C
authors.initials: MC
authors.lastname: Sousa
authors.affiliation: Department of Chemical and Biological Engineering, University of Colorado, Campus Box 596, Boulder, CO, 80309, USA. joel.kaar@colorado.edu.
authors.forename: Joel L
authors.initials: JL
authors.lastname: Kaar
mesh_terms: D001412:Bacillus subtilis / Q000201:enzymology; D001665:Binding Sites; D055162:Biocatalysis; D007093:Imidazoles / Q000737:chemistry*; D052578:Ionic Liquids / Q000737:chemistry*; D008049:Lipase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D056004:Molecular Dynamics Simulation; D016297:Mutagenesis, Site-Directed; D017434:Protein Structure, Tertiary
chemical_list: D007093:Imidazoles; D052578:Ionic Liquids; C502841:1-butyl-3-methylimidazolium chloride; D008049:Lipase
keywords: biocatalysis; butylmethylimidazolium chloride; crystallography; ionic liquids; lipase