Biochemistry 4th Edition by Christopher Mathews,Kensal van Holde, Dean Appling, Spencer Anthony Cahill

Exercise 8

Note that some of these problems refer to information presented in the Tools of Biochemistry 5A-D.
A protein has been sequenced after cleavage of disulfide bonds. The protein is known to contain 3 Cys residues, located as shown below. Only one of the Cys has a free -SH group and the other two are involved in an - S - S - bond.
The only methionine and the only aromatic amino acid (Phe) in this protein are in the positions indicated. Cleavage of the intact protein (i.e., with disulfide bonds intact) by either cyanogen bromide or chymotrypsin does noi break the protein into two peptides. Where is the - S - S - bond (AB, BC, or AC)