Affiliations 

  • 1 Institute of Biochemistry and Biophysics, University of Tehran, Tehran, Iran
  • 2 Faculty of Bioscience and Medical Engineering, University Technology Malaysia (UTM), Johor Bahru, Malaysia
  • 3 University of Trento, Department of Civil, Environmental and Mechanical Engineering, Via Mesiano, 77-38123 Trento, Italy
  • 4 Department of Molecular Medicine, National Institute for Genetics Engineering and Biotechnology, Tehran, Iran
  • 5 Department of Biophysics, Faculty of Basic Science, Science and Research Branch, Islamic Azad University, Tehran, Iran
  • 6 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
Int J Biol Macromol, 2016 Nov;92:1307-1312.
PMID: 26905468 DOI: 10.1016/j.ijbiomac.2016.02.045

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 H2O2 with 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.

* Title and MeSH Headings from MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.