Question

Peptide A and peptide B is linked by how many disulfide linkages in insulin?

• A. $1$
• B. $2$
• C. $3$
• D. $4$

Answer 1

The correct option is B $2$

Proinsulin is made up of 81 residues and formed by three distinct chains. The A chain, B chain, and the area connecting the two named the C peptide. The correct structure of proinsulin is crucial for the correct folding of mature insulin, as the placement of the C peptide sets the molecule up to create correctly positioned disulfide bonds in and between the A and B chains. There are three disulfide bonds that are necessary for mature insulin to be the correct structure. Two of these disulfide bonds are between the A and B chains, and one is an intra-A chain bond. The disulfide bonds occur between the seventh residues of the A and B chain, the 19th residue of the A chain and the 20th residue of the B chain, and the 6th and 11th residues of the A chain.

So the correct option is '2'.