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Thursday, May 6, 2021

Protein Folding- CSIR NET/ICMR/DBT (Life sciences)

Protein Folding

  • Protein folding is the physical process by which a polypeptide folds into its characteristics & functional three-dimensional 3D conformation.

  • The correct 3D structure is essential to protein function. Failure to fold into native structure produces inactive proteins.

  • A protein molecule folds spontaneously during/after biosynthesis. However, the process also depends on the nature of the solvent, the concentration of salts, the temperature, and the presence of molecular chaperones.

Protein Folding- CSIR NET/ICMR/DBT (Life sciences)


According to the experiment, which helps in the understanding of the protein folding was carried out by Biochemist Christian Anfinsen in 1960, that is the refolding of the protein ribonuclease A. 
  • Ribonuclease A isolated from the bovine pancreas is an enzyme that has a molecular weight (mw=13,700 Da) and it contains 124 amino acid residues and 4- disulfide linkages.

  • In the presence of a denaturant (Urea), and a reductant (reducing agent β-mercaptoethanol), Ribonuclease is denatured and the sulfide bonds are broken.

When the protein is allowed to renature by removing the denaturant and reductant (reducing agent), the protein regains its native confirmation, including 4 correctly paired disulfide bonds.

This finding provided the first evidence that;

  • However, when the reductant (reducing agent β-mercaptoethanol) is removed, while the denaturant (Urea) is still present, the disulfide bonds are formed again in protein but most of the disulfide bonds are formed between incorrect partners. This indicates that weak interactions are required for correct positioning of disulfide bonds and assumption of the native conformation.

Anfinsen's Experiment: Denaturation/Renaturation of Ribonuclease. Depending on the conditions for renaturation, we obtain either native ribonuclease or scrambled ribonuclease. 



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