Comparative Raman study of four plant metallothionein isoforms: Insights into their Zn(II) clusters and protein conformations

Mireia Tomas, Anna Tinti, Roger Bofill, Mercè Capdevila, Silvia Atrian, Armida Torreggiani

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11 Citations (Scopus)

Abstract

© 2016 Elsevier Inc. All rights reserved. Four Metallothioneins (MTs) from soybean (Glycine max) were heterologously synthesized and comparatively analysed by Raman spectroscopy. The participation of protein donor groups (S-thiol and N-imidazol) in Zn(II) chelation, as well as the presence of secondary structure elements was comparatively analysed. Metal clusters with different geometry can be hypothesised for the four GmMTs: a cubane-like or an adamantane-like metal cluster in Zn-GmMT1, and dinuclear Zn-S clusters in Zn-GmMT2, Zn-GmMT3 and Zn-GmMT4. The latter have also a similar average Cys/Zn content, whereas a lower ratio is present in Zn-GmMT1. This is possible thanks to the involvement in metal coordination of a greater number of bridging Cys, as well as of some carboxylate groups. As regards secondary structure elements, a large content of β-turn segments is present in all four Zn-GmMTs, especially for isoforms 1 and 4. β-strands give a contribution to the folding of three GmMTs isoforms, and the highest percentage was found in Zn-GmMT2 (-45%). Conversely, the α-helix content is negligible in all the GmMTs except in Zn-GmMT3, where this peculiar feature coincides with the possible involvement of the two His residues in metal coordination. Conversely, His is predominantly free and present as tautomer I in Zn-GmMT4. In conclusion, this work illustrates the attractive potential of Raman spectroscopy, combined with other techniques, to be a very informative tool for evidencing structural differences among in vivo synthesized metal-MT complexes.
Original languageEnglish
Pages (from-to)55-63
JournalJournal of Inorganic Biochemistry
Volume156
DOIs
Publication statusPublished - 1 Mar 2016

Keywords

  • His coordination
  • Metal cluster
  • Raman spectroscopy
  • Secondary structure
  • Zn-metallothionein

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