Proteins and Enzymes

ID #2109

When a protein gets denatured, does the disulfide bridge get broken too? Isn't the disulfide bridge like a covalent bond, and in class, I remember hearing that covalent bonds are like the strongest bond out of all the bonds that we learned so far.

You ask an excellent question, since covalent bonds are indeed very strong bonds. One thing to keep in mind is that not all proteins have disulfide bonds. Disulfide bonds only form between cysteine residues that are close enough together to form a bond. Cysteine residues are rare, and disulfide bonds are even rarer. If a protein has a disulfide bond, that bond is very important in stabilizing the protein's tertiary structure. Breaking that disulfide bond would facilitate the denaturation of the protein. Even though disulfide bonds are strong, they can be broken. In the laboratory setting, if a researcher wants to denature a protein with disulfide bonds he or she adds a special chemical reducing agent that breaks the disulfide bond to insure that the protein denatures completely. (That is obviously more information than you need to know for the test). For the purposes of this class, I think the main thing to remember is that denaturing protein results in the loss of ALL secondary and tertiary structure, and that would include the breaking of disulfide bonds.

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