title: A bio-mimetic zinc/tau protein as an artificial catalase.
abstract: In this study, the catalase-like activity of monomeric tau protein was reported in the presence of of zinc (Zn(II)) ions at low pH value. Monomeric tau protein contains two SH groups that are a target of disulfide bond formation. However these SH groups are able to interact with Zn(II) ion at pH 7.2 which creates a thiol bond as a mimetic model of chloroperoxidase active site which performs catalase like activity at low pH. Zn(II)/tau protein complex decomposed H2O2with a high rate (Vm) as well as an efficient turn oven number (kcat) at pH 3. This remarkable catalase like activity is may be attributed to the conformational reorientation of protein at low pH. Circular dichroism (CD) studies did not demonstrate any secondary structural changes of tau protein after addition of Zn(II) ions at pH 7.2. In addition, tau protein shows identical CD bands at pH 7.2 and 3. Moreover, fluorescence quenching of tau by Zn(II) at pH 7.2 was initiated by complex formation rather than by dynamic collision. A significant red shift (6nm) was observed in the emission maximum of the fluorescence spectra when the protein was dissolved at pH 3 compared to pH 7.2. This conformational change can provide information regarding the rearrangements of the protein structure and exposure of Cys-Zn(II) group to the solvent which induces easy access of active site to H2O2 molecules and corresponding enhanced catalytic activity of Zn(II)/tau protein complex. This study introduces tau protein as a bio-inspired high performing scaffold for transition metal encapsulation and introducing an engineered apoprotein-induced biomimetic enzyme.
authors.affiliation: Institute of Biochemistry and Biophysics, University of Tehran, Tehran, Iran.
authors.forename: Kazem
authors.initials: K
authors.lastname: Asadollahi
authors.affiliation: Institute of Biochemistry and Biophysics, University of Tehran, Tehran, Iran.
authors.forename: Neda Sadat Kazemein
authors.initials: NS
authors.lastname: Jasemi
authors.affiliation: Institute of Biochemistry and Biophysics, University of Tehran, Tehran, Iran.
authors.forename: Gholam Hossein
authors.initials: GH
authors.lastname: Riazi
authors.affiliation: Institute of Biochemistry and Biophysics, University of Tehran, Tehran, Iran.
authors.forename: Fatemeh Hedayati
authors.initials: FH
authors.lastname: Katuli
authors.affiliation: Faculty of Bioscience and Medical Engineering, University Technology Malaysia (UTM), Johor Bahru, Malaysia.
authors.forename: Fahimeh
authors.initials: F
authors.lastname: Yazdani
authors.affiliation: University of Trento, Department of Civil, Environmental and Mechanical Engineering, Via Mesiano, 77-38123 Trento, Italy.
authors.forename: Nasrin
authors.initials: N
authors.lastname: Sartipnia
authors.affiliation: Department of Molecular Medicine, National Institute for Genetics Engineering and Biotechnology, Tehran, Iran.
authors.forename: Mohammad Amin
authors.initials: MA
authors.lastname: Moosavi
authors.affiliation: Department of Biophysics, Faculty of Basic Science, Science and Research Branch, Islamic Azad University, Tehran, Iran.
authors.forename: Arash
authors.initials: A
authors.lastname: Rahimi
authors.affiliation: Department of Nanotechnology, Faculty of Advance Science and Technology, Pharmaceutical Sciences Branch, Islamic Azad University (IAUPS), Tehran, Iran. Electronic address: Falahati@ibb.ut.ac.ir.
authors.forename: Mojtaba
authors.initials: M
authors.lastname: Falahati
mesh_terms: D040761:Biomimetic Materials / Q000737:chemistry*; D002374:Catalase / Q000737:chemistry; D002413:Cations, Divalent; D002942:Circular Dichroism; D006801:Humans; D006861:Hydrogen Peroxide / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D010084:Oxidation-Reduction; D011485:Protein Binding; D017433:Protein Structure, Secondary; D012996:Solutions; D013050:Spectrometry, Fluorescence; D015032:Zinc / Q000737:chemistry*; D016875:tau Proteins / Q000737:chemistry*
chemical_list: D002413:Cations, Divalent; D012996:Solutions; D016875:tau Proteins; D006861:Hydrogen Peroxide; D002374:Catalase; D015032:Zinc
keywords: Catalase-like activity; Conformational changes; Zn(II)/tau protein