Improvement of Cd²⁺uptake ability of SmtA protein by Lys/Cys mutation; experimental and theoretical studies

Abstract

The improved Cd(2+) surface affinity characteristics of a mutated cyanobacterial metallothionein SmtA (K45C) were investigated via experimental and theoretical methods. Molecular dynamics simulations were carried out using a model of Cd(2+) and other ions enclosed in a fully hydrated simulation box with the wild-type or mutated SmtA protein. The theoretical results suggested that mutated SmtA was more powerful in absorption of Cd(2+) than the wild-type protein. Then, the mutated smtA gene (from Synechococcus PCC 7942) was synthesized by simplified gene synthesis method and expressed on isopropyl-beta-d-thiogalactopyranoside induction. The protein expression was investigated by SDS-PAGE and verified by Western blotting. Finally, cadmium uptake ratio of mutant protein toward wild type was analyzed by atomic absorption. This study is the first example of cytoplasmic expression of a mutant protein. Experimental results also verified that the mutation intensifies uptake of Cd(2+) ions.

Characterization of a putative ArsR transcriptional regulator encoded by Rv2642 from Mycobacterium tuberculosis

“…The uptake of metals is tightly regulated by metal-dependent transcription regulators to preclude the toxicity of excess metals (Saffar, Mehri, Mahnam, & Mobini-Dehkordi, 2015). SmtB/ArsR family metal-sensor proteins are transcriptional factors regulating the intracellular metal ion homeostasis.…”

A theoretical and experimental study of calcium, iron, zinc, cadmium, and sodium ions absorption by aspartame

“…For example, Friedman et al's study showed that a protein could sequester Na + ions [22]. Also, Saffar et al showed that a mutated SmtA protein could absorb cadmium ions [24]. In addition, experiments on ion Europium (III) absorption with the zwitterion form of amino acids by means of UV-Vis spectroscopy were studied by Heller et al [42].…”

“…Since the 1970s, advances in computer technology and algorithmic improvements has made MD simulation a valuable tool in many areas of science, such as proteins or nucleic acids [21]. Currently, conventional MD simulations are being used to study the interactions between proteins and ions in dilute salt solutions [22][23][24].…”