Disulfide Bonds

Abstract

A disulfide bond is a covalent bond between two sulfur atoms. Disulfide bonds are prevalent in biology and found in a range of biological molecules, for example between the sulfur atoms of protein cysteine residues. Protein disulfide bonds can fulfil a wide range of functions including promoting protein stability and regulating protein activity or function. Dedicated disulfide generating and transferring machineries that promote the introduction of disulfide bonds during oxidative protein folding can be found in the endoplasmic reticulum, mitochondrial intermembrane space and bacterial periplasm. Regulatory disulfide bonds are formed by different pathways to the structural disulfides. For example, hydrogen peroxide (H 2 O 2 ) may regulate protein activity by inducing the formation of disulfide bonds. In a few cases, H 2 O 2 may directly oxidise cysteine residues, but evidence is accumulating that thiol peroxidases may first react with H 2 O 2 and subsequently transfer their disulfide to specific target proteins. Key Concepts Disulfide bonds have multiple functions in proteins including instability and regulation of protein activity. Dedicated machineries to generate and transfer disulfide bonds to newly folding proteins are found in the endoplasmic reticulum, the mitochondrial intermembrane space and the bacterial periplasm. Cysteine residues in some proteins can react with H 2 O 2 leading to the formation of a disulfide bond that can regulate protein activity. Proteins that react efficiently with H 2 O 2 harbour specific mechanisms to increase the reaction efficiency. Thiol peroxidases can react extremely sensitively with H 2 O 2 leading to the formation of a disulfide bond. Thiol peroxidases can transfer their disulfide bond to specific target proteins. These peroxidase‐based redox relays may represent an important mechanism of H 2 O 2 ‐mediated protein oxidation.

New Insights into MeHg Accumulation in Rice (Oryza sativa L.): Evidence from Cysteine

“…EAAs cannot be synthesized by humans or animals and must be obtained from food sources. Cys belongs to NEAAs, and it functions in the folding and stabilizing of proteins through oxidation to form disulfide bonds, which are mainly present in proteins in the extracellular space or plasma membrane. , Cys is also a fundamental molecular for the synthesis of methionine, glutathione, and phytochelatins. , Cys can bind with Hg to affect its speciation and toxicity . Proline (Pro) and tyrosine (Tyr), which also belong to NEAAs, play crucial roles in antioxidant and osmolyte activities. , Pro pretreatment can alleviate Hg stress to rice seedlings by eliminating reactive oxygen species (ROS) .…”