Analysis of spectrometry and thermodynamics of the metallothionein in freshwater crab Sinopotamon henanense for its binding ability with different metals. (May 2020)

• Record Type: Journal Article
• Authors: Yang, Hui Zhen; Wang, Lu; He, Yong J.; Jing, Wei X.; Ma, Wen L.; Chen, Chien M.; Wang, Lan
• Is Part Of: Chemosphere. Volume 246(2020)
• Publication Date: 2020-05
• Subjects: Sinopotamon henanense -- Metallothionein -- Spectrometry -- Thermodynamics -- Metal binding ability -- Heavy metals; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2019.125670
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: The metal binding nature of heterologously expressed metallothionein of Sinopotamon henanense (ShMT) had been demonstrated previously. In this study, we analysed the stoichiometry of ShMT yielded in vivo and exchange reactions of the Zn-ShMT with Cd 2+, Pb 2+ and Cu 2+ in vitro via electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS), circular dichroism (CD) spectroscopy, inductively coupled plasma mass spectrometry (ICP-MS), and isothermal titration calorimetry (ITC). The results of ESI-TOF-MS analyses showed that metal-ShMT synthesized in vivo had three major forms, namely Zn15 -, Cd9 -, and Pb5 -ShMT. The ITC analyses of exchange reactions demonstrated that Zn-ShMT exhibited up to 6, 6, and 7 binding sites for Cd 2+, Pb 2+ and Cu 2+ . By the analyses of the UV and CD spectra in the substitution experiments showed that the geometric structural stability of metal-ShMT could be influenced when excess of over 6, 6, or 7 equivalents of Cd 2+, Pb 2+, or Cu 2+ were added into Zn-ShMT. Although both the reconstructed apo-ShMT and substituted Zn-ShMT with three metal ions fitted the same M6 Ⅱ- and M7 Ⅰ-ShMT binding models for divalent and monovalent metals, the differences in their thermodynamic data suggested that discrepancies exit in their physiological functions. These results suggested that ShMT yielded in vivo had a higher storage capability for Zn 2+ and a uptake ability for Cd 2+, and Zn-ShMT was more easy to release Zn 2+ as well as to uptake Cd 2+, Cu 2+, or Pb 2+ . The results presented in this work will be very valuable to understand the function(s) of ShMT not only in a normal physiological condition but also in the presence of non-essential metals in crabs. Highlights: ShMT synthesized in Zn 2+ and Cd 2+ containing medium manifested mainly Zn15 - and Cd9 -ShMT species. ShMT in Sinopotamon. henanense could largely stockpile Zn 2+ and uptake Cd 2+ . Zn-ShMT could bind with Cd 2+ and Pb 2+ via the metal binding model of M6 Ⅱ-ShMT, but with Cu 2+ via M7 Ⅰ-ShMT. Zn-ShMT could release Zn 2+ and could uptake Cd 2+, Cu 2+, or Pb 2+ . Zn-ShMT could mediate the inter-regional Zn 2+ transfer and serve as a biomolecule for detoxification of other metal ions.