title: Conformational changes and orientation of Humicola lanuginosa lipase on a solid hydrophobic surface: an in situ interface Fourier transform infrared-attenuated total reflection study.
abstract: This study was done to better understand how lipases are activated at an interface. We investigated the conformational and solvation changes occurring during the adsorption of Humicola lanuginosa lipase (HLL) onto a hydrophobic surface using Fourier transform infrared-attenuated total reflection spectroscopy. The hydrophobic surfaces were obtained by coating silicon attenuated total reflection crystal with octadecyltrichlorosilane. Analysis of vibrational spectra was used to compare the conformation of HLL adsorbed at the aqueous-solid interface with its conformation in solution. X-ray crystallography has shown that HLL exists in two conformations, the closed and open forms. The conformational changes in HLL caused by adsorption onto the surface were compared with those occurring in three reference proteins, bovine serum albumin, lysozyme, and alpha-chymotrypsin. Adsorbed protein layers were prepared using proteins solutions of 0.005 to 0.5 mg/mL. The adsorptions of bovine serum albumin, lysozyme, and alpha-chymotrypsin to the hydrophobic support were accompanied by large unfoldings of ordered structures. In contrast, HLL underwent no secondary structure changes at first stage of adsorption, but there was a slight folding of beta-structures as the lipase monolayer became complete. Solvation studies using deuterated buffer showed an unusual hydrogen/deuterium exchange of the peptide CONH groups of the adsorbed HLL molecules. This exchange is consistent with the lipase being in the native open conformation at the water/hydrophobic interface.
authors.affiliation: Laboratoire de Dynamique, Interactions et Réactivité, Centre National de la Recherche Scientifique, Université Paris 6, 94320 Thiais, France. sylvie.noinville@glvt-cnrs.fr
authors.forename: Sylvie
authors.initials: S
authors.lastname: Noinville
authors.forename: Madeleine
authors.initials: M
authors.lastname: Revault
authors.forename: Marie-Hélène
authors.initials: MH
authors.lastname: Baron
authors.forename: Ali
authors.initials: A
authors.lastname: Tiss
authors.forename: Stéphane
authors.initials: S
authors.lastname: Yapoudjian
authors.forename: Margarita
authors.initials: M
authors.lastname: Ivanova
authors.forename: Robert
authors.initials: R
authors.lastname: Verger
mesh_terms: D000577:Amides / Q000737:chemistry; D001203:Ascomycota / Q000201:enzymology*; D002918:Chymotrypsin / Q000737:chemistry; D018360:Crystallography, X-Ray; D003903:Deuterium; D007700:Kinetics; D008049:Lipase / Q000737:chemistry*; D008958:Models, Molecular; D009113:Muramidase / Q000737:chemistry; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012710:Serum Albumin, Bovine / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods; D013499:Surface Properties
chemical_list: D000577:Amides; D012710:Serum Albumin, Bovine; D003903:Deuterium; D008049:Lipase; D009113:Muramidase; D002918:Chymotrypsin