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When two amino acids bond to each other through their side chains, they normally do so through a disulfide bond. The particular side chain involved is the thiol group (- S H). Oxidation of the thiol group yields a disulfide (S-S) bond. The presence of S-S then helps to maintain the tertiary structure of the protein. An amino acid that commonly forms S-S bonds in proteins in cysteine. When two cysteines are bonded by an S-S bond, the resulting molecule between the two protein chains is called cystine. The figure below shows the formation of a disulfide bond. The R on each side group represents the remainder of the amino acid.
R R | | SH S oxidation-> | + 2H SH S | | R RIn proteins that contain more than one disulfide bond, proper pairing of the cysteine residues is important for normal structure and activity.
Disulfide bonds play an imporant protective role for bacteria as a reversible switch that turns a protein on or off when bacterial cells are exposed to oxidation reactions. Hydrogen peroxide ( H2 O2) in particular can severely damage DNA and kill the bacteriumActinobacteria Aquificae Bacteroidetes/ Chlorobi Chlamydiae/ Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/ Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Omnibac at low concentrations if it weren't for the protective action of the SS-bond.
Disulfide bonds also play a significant role in the vulcanizationVulcanization is the process of cross-linking elastomer molecules to make the bulk material harder, less soluble and more durable. It is also called curing. It is the heart of the art and science of rubber compounding. Vulcanization is a chemical process of rubberThis article is about the material rubber, for other uses see Rubber (disambiguation Rubber is an elastic hydrocarbon polymer which occurs as a milky emulsion (known as latex) in the sap of a number of plants but can also be produced synthetically. The ma.
In eukaryoticEukaryotes are organisms with complex cells, in which the genetic material is organized into membrane-bound nuclei. They include the animals, plants, and fungi, which are mostly multicellular, as well as various other groups called protists, many of which cells, disulfide bonds are formed in the lumen of the RER (rough endoplasmic reticulum) but not in the cytosolThe cytosol (as opposed to cytoplasm which also includes the organelles) is the internal fluid of the cell, and a large part of cell metabolism occurs here. Proteins within the cytosol play an important role in signal transduction pathways, glycolysis, an. Thus disulfide bonds are found only in secretory proteins, lysosomal proteins, and the exoplasmic domains of membrane proteins.