Question

Imagine that you have just isolated a peptide hormone with the following primary sequence:

MLSCRLQEALAALSKIVLADLGCVTGAPSDPR

(Assume the protein is in solution at physiological pH, and remember to include the amino acids at each end of the chain. A charge may come from the R-group, the N-terminus, and/or the C-terminus. If a residue occurs more than once, include each one in your answer.)

List the residues (individual amino acids) that contribute a positive charge: ​
List the residues that contribute a negative charge: ​
Which residues can be connected by a disulfide bond? (Only type the letter.) ​
What would the NET charge of this peptide be at physiological pH?

Answer 1

- residues that contribute positive charges : histidine(H), lysine(K), arginine(R).

- residues that contribute negative charges : aspartic acid(D), glutamic acid(E).

- the residues that can be connected by disulphide bond is cysteine (C).

- net charge : zero