Question

Which of the 20-amino acid sequences listed below is the most likely candidate to be the transmembrane segment in a protein that spans the membrane exactly once? a) I T L I Y F G V M A G V I G T I L L I S b) I T P I Y F G P M A G V I G T P L L I S c) I T E I Y F G R M A G V I G T D L L I S. Explain your choice.

Answer 1

Correct option is A. ITLIYFGVMAGVIGTILLIS

Explanation:
Peptide B contains three prolines (P) which disturb the alpha helix structure
Peptide C contains a glutamic acid (E), arginine (R), and aspartic acid (D) which are charged residues which is not compatible with the hydrophobic environment a transmembrane segment is in.
Peptide A has no charged residues and mostly non-polar residues and is therefore most compatible with the hydrophobic environment of a transmembrane segment.