ABSTRACT
Metallothioneins' (MTs) biological function has been a matter of debate since their discovery. The importance to categorize these cysteine-rich proteins with high coordinating capacity into a specific group led to numerous classification proposals. We proposed a classification based on their metal-binding abilities, gradually sorting them from those with high selectivity towards Zn/Cd to those that are Cu-specific. However, the study of the NpeMT1 and NpeMT2isoforms of Nerita peloronta, has put a new perspective on this classification. N. peloronta has been chosen as a representative mollusk to elucidate the metal-binding abilities of Neritimorpha MTs, an order without any MTs characterized recently. Both isoforms have been recombinantly synthesized in cultures supplemented with ZnII, CdII, or CuII, and the purified metal-MT complexes have been thoroughly characterized by spectroscopic and spectrometric methods, leading to results that confirmed that Neritimorpha share Cd-selective MTs with Caenogastropoda and Heterobranchia, solving a so far unresolved question. NpeMTs show high coordinating preferences towards divalent metal ions, although one of them (NpeMT1) shares features with the so-called genuine Zn-thioneins, while the other (NpeMT2) exhibits a higher preference for Cd. The dissimilarities between the two isoforms let a window open to a new proposal of chemical MT classification.
Subject(s)
Cadmium/metabolism , Gastropoda/metabolism , Metallothionein/chemistry , Metallothionein/classification , Zinc/metabolism , Animals , Circular Dichroism , Copper/metabolism , Escherichia coli/genetics , Gastropoda/chemistry , Metallothionein/genetics , Metallothionein/metabolism , Protein Domains , Protein Isoforms , Recombinant Proteins/genetics , Recombinant Proteins/metabolism , Spectrophotometry, UltravioletABSTRACT
Abstract: Samples of terrestrial gastropods were collected year-round in seven caves in Presidente Olegário municipality, Minas Gerais state, southeastern Brazil, during several expeditions from 2012 to 2014. Twenty-four taxa (plus a single freshwater species), mainly stylommatophorans, were found in the material. The following species are reported for the first time for Minas Gerais state: Alcadia iheringi Wagner, 1910 and Helicina sordida King, 1831 (Helicinidae); Cecilioides consobrina (d'Orbigny, 1841) (Ferussaciidae); Entodina gionensis Morretes, 1940 and Scolodonta interrupta (Suter, 1900) (Scolodontidae); Megalobulimus sanctipauli (Ihering & Pilsbry, 1900) (Strophocheilidae); Drymaeus coarctatus (Pfeiffer, 1845) (Bulimulidae); Habroconus semenlini (Moricand, 1846) (Euconulidae); and Solaropsis aff. rosaria (Pfeiffer, 1849) (Solaropsidae). Furthermore, the species Drymaeus iracema (Simone, 2015) and Drymaeus terreus (Simone, 2015) are synonymized with Drymaeus coarctatus (L. Pfeiffer, 1845).
Resumo: Amostras de gastrópodes terrestres foram coletadas em sete cavernas na região do município de Presidente Olegário, Minas Gerais, Brasil, durane múltiplas expedições ao longo dos anos de 2012 a 2014. Vinte-e-quatro táxons (mais uma única espécie dulciaquícola) foram encontrados, em sua maioria Stylommatophora. As seguintes espécies são aqui reportadas pela primeira vez para o estado de Minas Gerais: Alcadia iheringi Wagner, 1910 e Helicina sordida King, 1831 (Helicinidae); Cecilioides consobrina (d'Orbigny, 1841) (Ferussaciidae); Entodina gionensis Morretes, 1940 e Scolodonta interrupta (Suter, 1900) (Scolodontidae); Megalobulimus sanctipauli (Ihering & Pilsbry, 1900) (Strophocheilidae); Drymaeus coarctatus (Pfeiffer, 1845) (Bulimulidae); Habroconus semenlini (Moricand, 1846) (Euconulidae); e Solaropsis aff. rosaria (Pfeiffer, 1849) (Solaropsidae). Além disso, as espécies Drymaeus iracema (Simone, 2015) e Drymaeus terreus (Simone, 2015) são aqui sinonimizadas com Drymaeus coarctatus (L. Pfeiffer, 1845).
ABSTRACT
The identity of Helicina mediana Gassies, 1870 was clarified by the study of the type material and the selection of a lectotype. It is currently classified as Sturanya mediana (Gassies, 1870) and replaces the temporarily applied name Sturanya novaecaledoniae (Baird, 1873) for the medium sized helicinid species widely spread in the north-eastern part of mainland New Caledonia and the adjacent Îles Belep. The latter name and Helicina nehoueensis Hartman 1889 are synonyms of S. mediana.
