Question

1. Does the discovery of chaperones make the Anfinsen experiment incorrect?

2. Some proteins can be purified, denatured, and refold in the tube but the same protein requires chaperones to fold in the cell. Why do you think this is the case?

3. Eating only vegan will put you at risk for deficiency in which two amino acids? How does meat provide us with these amino acids?

Answer 1

1.

Anfinsen 's experiment shows that the protein folding is innate in the amino acid sequence of the proteins. The amino acids present will develop bonds between them based on the charge and the hydrophobicity etc. The discovery of chaperons does not completely negate the Anfensen's dogma.

This is because, though chaperons are needed for protein folding with in the cell, they are not important in the folding under lab conditions. Chaperons protect the folding polypeptides from other protein molecules in the cell. This is how proteins are protected from other molecules and also protected from forming aggregates with in the cell and allowing the polypeptide to correctly fold. So chaperon discovery does not negate the Anfensen's dogma.

2. The conditions within the cell are different from the conditions in the test tube. In the cell the concentration of the protein synthesized will be high and there are chances of the proteins forming aggregates instead of folding because of the hydrophobic interactions that they develop between different molecules. Such formation of aggregates will will disturb the cellular processes. So chaperons will prevent such aggregation of proteins with in the cell and help in correct folding by shielding the protein from others.

Another reason for the requirement of chaperons inside cell is that the partially folded proteins may be considered as misfolded proteins and protein degradation may start resulting in protein destruction.

3. Vegans consume only plant based food. The plant based foods are deficient in some essential amino acids. These include primarily, Lysine and Methionine. The microbes that reside in the gut of the cattle provide all essential amino acids needed for the cattle. So lysine and methionine are also produced by the microbes residing in the cattle.