Question

What happens to a protein or nucleic acid if it is denatured?

Answer 1

If a protein or nucleic acid is denatured, it loses its secondary or tertiary structure.

Explanation:

Denaturing changes the shape of a protein or nucleic acid although it does not change the primary amino acid sequence, also known as the primary structure. To break the primary structure, peptide bonds would need to be broken, and denaturing does not do this.

Denaturing can happen when a protein or nucleic acid is exposed to heat or chemicals such as ethanol, formaldehyde, sodium bicarbonate, and others.

Cooking food for example denatures some of the proteins in the food, making it easier to digest. Changing the shape of the protein changes how that protein will interact with its environment.

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The opposite of denaturation is renaturation, when the protein or nucleic acid regains its secondary and or tertiary structure. This is not always possible.

An example of denaturation and renaturation is when Anfinsen denatured ribonuclease.

He used `beta`-mercaptoethanol (reducing agent) and urea (chaotropic agent) at the same time, removing all enzymatic activity. Then, when he slowly removed both at the same time, the protein's disulfide bonds could reform in their proper locations as the protein re-folded in an oxidizing environment, thereby returning its enzymatic activity to `100%`.

Had Anfinsen removed the `beta`-mercaptoethanol slowly first, and then later removed urea, the disulfide bonds would have reformed at random and thus given poor enzymatic activity recovery (`~10%`).

Concept (but not wording) from Fundamentals of Biochemistry, Voet, Voet, and Pratt.