Among the trace elements, zinc is one of the most used elements in biological systems. Zinc is found in the structure of more than 2700 enzymes, including hydrolases, transferases, oxyreductases, ligases, isomerases, and lyases. Not surprisingly, it is present in almost all body cells. Preserving the stability and integrity of biological membranes and ion channels, zinc is also an intracellular regulator and provides structural support to proteins during molecular interactions. It acts as a structural element in nucleic acids or other gene-regulating proteins. Metallothioneins, the low molecular weight protein family rich in cysteine groups, are involved significantly in numerous physiological and pathological processes including particularly oxidative stress. A critical role of metallothioneins (MT) is to bind zinc with high affinity and to serve as an intracellular zinc reservoir. By releasing free intracellular zinc when needed, MTs mediate the unique physiological roles of zinc. MT expression is induced by zinc elevation, and thus, zinc homeostasis is maintained. That MT mediates the effects of zinc, besides having strong radical scavenging effects, points to the critical part it plays in oxidative stress. The present review aims to give information on metallothioneins, which have critical importance in the metabolism and molecular pathways of zinc.

Zinc, which is involved in the structure of all enzyme classes, is a micro nutrient element and necessary for growth and development. The ability of zinc to function without causing toxic effects is depends on the protection of its homeostasis. Zinc transporter proteins are responsible for keeping zinc at certain concentrations. Based on their predicted membrane topology, Zn transporters are divided into two major families, SLC39s/ZIPs and SLC30s/ZnTs, which transport Zn in opposite directions through cellular and intracellular membranes. ZIPs increases the zinc concentration in the cytosol. For this, the ZIPs carries the zinc from extracellular and intracellular compartments to the cytosol. ZnTs, reduces the concentration of zinc in the cytosol. For this, ZnTs carries the zinc from the cytosol to extracellular and intracellular compartments. After being transported to the cell, 50% of the zinc is found in the cytoplasm, 30-40% in the nucleus, and 10% in the plasma and organelle membranes. The expression of many zinc transporter proteins in the cell is depending on the concentration of zinc and the physiological problems. The aim of this study is to give information about association of zinc transporter proteins with physiological events and health problems.

Zinc finger (ZnF) proteins are the largest transcription factors family. They constitute of nine subgroups including Cys2His2, Cys3His, Cys3HisCys4, Cys2HisCys5, Cys4HisCys3, Cys2HisCys, Cys4, Cys6 and Cys8. ZnFs perform tasks of recognizing DNA, packaging RNA, transcriptional activity, regulating apoptosis, folding and collecting proteins, and binding lipids. One of the largest subgroups of these proteins is ZF-Cys2His2, containing SIZ1, ZAT, ZAT7, ZFP1, ZFP252, DST, ZFP1, SIZF3, ZFP179, ZjZFN1, SICZFP1, and ZF-Cys2His2 proteins are found in plants tissues and fulfill important tasks in their defense to struggle with biotic and abiotic stresses (i.e., salt, drought, cold, oxidative). The aim of this chapter is to reveal importance of ZF-Cys2His2 proteins against various stress conditions.