title: Comparative Raman study of four plant metallothionein isoforms: Insights into their Zn(II) clusters and protein conformations.
abstract: 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.
authors.affiliation: Dep. Genètica, Facultat de Biologia,Univ. Barcelona, Av. Diagonal 645, 8028-Barcelona, Spain; Dep. Química, Facultat de Ciències, Univ.Autònoma de Barcelona, E-08193 Bellaterra, Barcelona, Spain.
authors.forename: Mireia
authors.initials: M
authors.lastname: Tomas
authors.affiliation: Dipartimento di Scienze Biomediche e Neuromotorie, Università di Bologna, Via Belmeloro 8/2, 40126 Bologna, Italy.
authors.forename: Anna
authors.initials: A
authors.lastname: Tinti
authors.affiliation: Dep. Química, Facultat de Ciències, Univ.Autònoma de Barcelona, E-08193 Bellaterra, Barcelona, Spain.
authors.forename: Roger
authors.initials: R
authors.lastname: Bofill
authors.affiliation: Dep. Química, Facultat de Ciències, Univ.Autònoma de Barcelona, E-08193 Bellaterra, Barcelona, Spain.
authors.forename: Mercè
authors.initials: M
authors.lastname: Capdevila
authors.affiliation: Dep. Genètica, Facultat de Biologia,Univ. Barcelona, Av. Diagonal 645, 8028-Barcelona, Spain.
authors.forename: Silvia
authors.initials: S
authors.lastname: Atrian
authors.affiliation: Istituto I.S.O.F., Consiglio Nazionale delle Ricerche, Via P. Gobetti 101, 40129 Bologna, Italy. Electronic address: armida.torreggiani@isof.cnr.it.
authors.forename: Armida
authors.initials: A
authors.lastname: Torreggiani
mesh_terms: D000595:Amino Acid Sequence; D008668:Metallothionein / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism*; D011487:Protein Conformation; D020033:Protein Isoforms / Q000737:chemistry / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D013059:Spectrum Analysis, Raman / Q000379:methods*; D015032:Zinc / Q000378:metabolism*
chemical_list: D010940:Plant Proteins; D020033:Protein Isoforms; D008668:Metallothionein; D015032:Zinc
keywords: His coordination; Metal cluster; Raman spectroscopy; Secondary structure; Zn-metallothionein