Navigation Links
Disulfide bond


A disulfide bond (SS-bond), also called a disulfide bridge, is a strong covalent bond between two sulfhydryl groups. This bond is very important to the folding, structure, and function of proteins.

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 sulfhydryl group (-SH). 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                R 

In proteins that contain more than one disulfide bond, proper pairing of the cysteine residues is important for normal structure and activity.

Contents

In bacteria

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 (H2O2) in particular can severely damage DNA and kill the bacterium at low concentrations if it weren't for the protective action of the SS-bond.

In rubber

Disulfide bonds also play a significant role in the vulcanization of rubber.

In eukaryotes

In eukaryotic cells, disulfide bonds are formed in the lumen of the RER (rough endoplasmic reticulum) but not in the cytosol. Thus disulfide bonds are found only in secretory proteins, lysosomal proteins, and the exoplasmic domains of membrane proteins.

Disulphide bonds are also formed within and between protamines in the sperm chromatin of many mammalian species.

In hair

Hair is a biological polymer, with over 90% of its dry weight made of proteins called keratins. Under normal conditions, human hair contains around 10% water, which modifies its mechanical properties considerably. Hair proteins are held together by disulfide bonds, from the amino acid cysteine. These links are very robust: for example, virtually intact hair has been recovered from ancient Egyptian tombs. Different parts of the hair have different cysteine levels, leading to harder or softer material. Breaking and making disulfide bonds governs the phenomenon of wavy or frizzy hair.

External links


'"/>


(Date:12/19/2014)... Dec. 18, 2014 Research and Markets ... of the "iPhone 5S Fingerprint Sensor - ... report to their offering. ... of AuthenTec in July 2012, Apple introduced the ... is currently the only device of Apple incorporating ...
(Date:12/19/2014)... Dec. 18, 2014  23andMe, Inc., the leading personal ... that pinpoints fine-scale differences in genetic ancestry of individuals ... Since immigrants first arrived more than four ... has served as a meeting place for peoples ... and the ongoing mixing of peoples with African, European, ...
(Date:12/17/2014)... , Dec. 15, 2014 Research and ... the addition of the "Samsung Galaxy S5 ... report to their offering. ... a totally different sensing technology than the iPhone ... fingerprint sensor in its product. The ...
Breaking Biology News(10 mins):iPhone 5S Fingerprint Sensor - Apple/AuthenTec TMDR92 & Sapphire - Technology Report 223andMe Study Sketches Genetic Portrait of the United States 223andMe Study Sketches Genetic Portrait of the United States 323andMe Study Sketches Genetic Portrait of the United States 4Samsung Galaxy S5 - Home Button Synaptics Fingerprint Sensor Technology Analysis 2
... MD FASEB MARC (Maximizing Access to Research Careers) ... American College of Sports Medicine (ACSM) Texas Regional Chapter ... These awards are meant to promote the entry of ... the mainstream of the basic science community and to ...
... cross the Atlantic Ocean to get to the Sargasso Sea to ... them from predators, researchers from the University of Southern Denmark report: ... The European eel is in decline, and all over the world ... to bring its numbers back up. One of the great puzzles ...
... Medical Research have glimpsed two proteins working together inside ... and its exterior compartment, the cytoplasm. The research provides ... found in organisms from yeast to humans does its ... Sue Jaspersen, Ph.D., focused on a protein called Ndc1, ...
Cached Biology News:Threatened eels disappear in the deep on their way to the Sargasso Sea 2Conserved nuclear envelope protein uses a shuttle service to travel between job sites 2Conserved nuclear envelope protein uses a shuttle service to travel between job sites 3
Other biology definitionOther Tags