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Abiotic stress response in yeast and metal-binding ability of a type 2 metallothionein-like protein (PutMT2) from Puccinellia tenuiflora

Zhang, Min, Takano, Tetsuo, Liu, Shenkui, Zhang, Xinxin
Molecular biology reports 2014 v.41 no.9 pp. 5839-5849
Escherichia coli, Puccinellia, abiotic stress, aluminum, arsenic, atomic absorption spectrometry, barium, cadmium, chromium, cobalt, copper, gene overexpression, genes, glutathione transferase, hydrogen peroxide, iron, lead, magnesium, manganese, metabolism, metal tolerance, nickel, proteins, salinity, silver, sodium, sodium chloride, stress response, transgenic plants, yeasts, zinc
Metallothioneins are low-molecular weight and cysteine-rich metal-binding proteins that play predominant cellular roles in the scavenging of reactive oxygen species and in mediating metal metabolism. To evaluate the role of a type-2 metallothionein-like gene from Puccinellia tenuiflora (PutMT2), the gene was over-expressed in yeast, and growth was assessed under a variety of abiotic stress conditions including peroxide (H₂O₂), salinity (NaCl and NaHCO₃), and metal stress. PutMT2 overexpression in yeast improved the tolerance of cells to H₂O₂, NaCl, NaHCO₃, Zn²⁺, Fe²⁺, Fe³⁺, Cd²⁺, Cr⁶⁺, and Ag⁺, but increased the sensitivity of cells to Mn²⁺, Co²⁺, Cu²⁺, and Ni²⁺ compared with control cells. PutMT2 was then expressed in Escherichia coli BL21as a glutathione S-transferase (GST) fusion protein (GST-PutMT2), and the metal-binding ability of GST-PutMT2 was analyzed and compared with GST alone using inductively coupled plasma atomic emission spectroscopy. Results showed that PutMT2 could bind to Cr, Cd, Co, Ag, Ba, Pb, Mn, Zn, Fe, Cu, P, Al, and Mg, but not Ni and As. There was no evidence to suggest that PutMT2 exhibited a specific or selective binding tendency to any individual metal ion. PutMT2 protein bound to Zn, Na, and Cu in vivo, perhaps with the highest affinity for Cu. Taken together, our results suggest that PutMT2 protein could play an important role in improving metal tolerance by metal binding in yeast. However, additional studies are required to confirm these results and to clarify the function of PutMT2 in transgenic plants.