title: Photo-induced unfolding and inactivation of bovine carbonic anhydrase in the presence of a photoresponsive surfactant.
abstract: Photoreversible changes in the conformation and enzymatic activity of bovine carbonic anhydrase have been investigated as a function of photoresponsive surfactant concentration and light conditions. The light-responsive surfactant undergoes a photoisomerization from the relatively hydrophobic trans isomer under visible light to the relatively hydrophilic cis isomer upon UV illumination, providing a means to photoreversibly control enzyme-surfactant interactions. Small-angle neutron scattering and dynamic light scattering measurements, along with fluorescence spectroscopy, indicate that carbonic anhydrase unfolds upon addition of the surfactant under visible light, while only a small degree of unfolding is observed under UV light. Therefore, the enzyme is completely inactivated in the presence of the trans surfactant, while 40% of the native activity is preserved under UV light, providing a photoreversible "on/off switch" of enzyme activity. Small-angle neutron scattering data provide details of the in vitro conformational changes of the enzyme in response to the photosurfactant and light, with the enzyme found to aggregate as a result of photosurfactant-induced unfolding. Fourier transform infrared (FT-IR) spectroscopy further provides information on the secondary structure changes of the protein in the presence of photosurfactant.
authors.affiliation: Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, CA 90089-1211, USA.
authors.forename: Panteha
authors.initials: P
authors.lastname: Mirarefi
authors.forename: C Ted
authors.initials: CT
authors.lastname: Lee
mesh_terms: D000818:Animals; D002256:Carbonic Anhydrases / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects*; D002417:Cattle; D033363:Neutron Diffraction; D011487:Protein Conformation / Q000528:radiation effects; D017510:Protein Folding / Q000528:radiation effects; D017433:Protein Structure, Secondary / Q000187:drug effects; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology; D012542:Scattering, Radiation; D053838:Scattering, Small Angle; D013501:Surface-Active Agents / Q000494:pharmacology*
chemical_list: D000644:Quaternary Ammonium Compounds; D013501:Surface-Active Agents; C006664:4-azobenzenetrimethylammonium; D002256:Carbonic Anhydrases