Question

Assume that the average molecular mass of an amino acid 112, and that 4 ATP equivalents are expended to form a peptide bond. Using the current model for protein folding in GroEL/ES, compare the cost of protein synthesis with the cost of protein folding for a 70-kD polypeptide in E. coli.

Answer 1

It is given that fro one peptide bond 4 ATP are used. A peptide bond is formed between 2 amino acids.

The given weight of the protein is 70 kD. The weight of one amino acid is 1000 Da. So 70 kD will have 70000 Da. So there will be 70 amino acids in this 70 kD protein.

So there will be total 69 bonds formation in total protein. One bond is equal to 4 ATP.

69 bonds formation will use 69*4 = 276 ATP.

The folding of protein using GroEL/ES only uses 2 ATP.

So total 276 ATP are used in protein synthesis and only 2 ATP are used in protein folding.