A state of the art review on characterization of heavy metal binding metallothioneins proteins and their widespread applications

Highlights: • ELISA, HPLC and RIA have been employed for quantifying kinetics of metal accumulation in marine animals • Size exclusion and Anion exchange chromatography along with capillary electrophoresis have been used for sample preparation • ELISA, RIA, FIA, and western blotting have been used for estimation of metallothioneins • Applications of metallothioneins include serving as biomarkers, making biosensors and heavy metal remediation Metallothioneins (MTs) are small metalloproteins that contain cysteine residues and provide excellent feasibility for binding metals. They have low molecular mass and are known to carry out a plethora of functions including metal homeostasis, scavenging free radicals, and shield against heavy metals. The expression levels of these peptides among invertebrates and aquatic vertebrates have compelled researchers all over the world to study MTs as a promising solution for resolving heavy metal contamination. The role of MTs in cadmium disposition, poisoning, toxicity, carcinogenesis, and its biokinetics have been exhaustively studied, along with the various analytical methods used to characterize these peptides. Although, classically, various natural biological processes are being carried out by these metal-binding proteins, they are now being exploited as bio-environmental markers for predicting heavy metal contamination based on their levels of expression. This review focuses on MTs by elaborating on its structural and chemical characterization, a comprehensive overview of the notable techniques being utilized for quantification and purification of such peptides and its applications in various fields.