Question

Which one of the following statements about protein structure is correct?

• A. Proteins consisting of one polypeptide can have quaternary structure.
• B. The formation of a disulphide bond in a protein requires that the two participating cystine residues be adjacent to each other in the primary sequence of the protein.
• C. The stability of quaternary structure in proteins is mainly due to covalent bonds among the subunits.
• D. The information required for the correct folding of a protein is contained in the specific sequence of amino acids along the polypeptide chain.

Answer 1

Answer: (D)

The correct folding of a protein is guided by specific interactions among the side chains of the amino acid residues of a polypeptide chain. The two cystine residues that react to form the disulphide bond may be a great distance apart in the primary structure (or on separate polypeptides) but are brought into close proximity by the three-dimension folding of the polypeptide chain.