Given the following peptide sequence LARYNMTQGRCKPVNTFVMHEPL

Given the following peptide sequence: LARYNMTQGRCKPVNTFVMHEPLVDVQNVCFKEAAAK

a) how many disulfide bonds do you expect to find? And how many different possible arrangements of disulfide bonds are possible in this peptdie?

b) which exopeptidase could you use to determine the C-terminal amino acid?

Solution

a) There is one disulfide bond present in the given sequence. The cysteine present at position 11 and 30 forms a disulfide bridge. The distance between the bonds is 19 and the bond is MTQGRCKPVNT-DVQNVCFKEAA.
There seems to be only one possible arrangement in the given peptide.

b) As the C-terminus amino acid here is Lysine, Carboxypeptidase would be used as they cleave the C-terminal residue. Carboxypeptidase C or carboxypeptidase B would be preferred.