Question

Which of the following peptides can form both inter- and intra-molecular disulfide bonds? Inter- means between molecules and intra- means within the molecule.

A. ACTPHE

B. ECMCWF

C. ISTYG

D. MKNQ

E. None of the above

Answer 1

Ans - E

A disulfide bond is also called as S-S bond or disulphide bridge. It is a covalent bond derived from two thiol groups. The formation of disulphide bond mostly occurs with the thiol groups in cysteine. Disulfide bonds can occur two ways: intramolecular and intermolecular disulfide bonds.

Intramolecular disulfide bonds occur within a polypeptide chain and are responsible for stabilizing tertiary structures of proteins whereas intermolecular disulfide bonds occur between polypeptide chains and are responsible for quaternary proteins structures.

In the above question, all the options A,B,C and D are showing a single polypeptide chain therefore both inter and intramolecular disulfide bond together in one polypeptide chain is not possible.