Question

The amino acid sequences below represent the sequences of transmembrane helices. The characteristics of α helices that form a channel are different from those that form a single transmembrane domain. Which helix forms a single transmembrane domain?

1) Helix A
2) Helix B
3) Helix C
4) Helix D

Answer 1

Given the characteristics of alpha-helices in transmembrane proteins, the helix with the most non-polar and hydrophobic amino acids would be indicative of a single transmembrane domain, as these domains do not typically form channels or pores.

Step-by-step explanation:

To determine which helix forms a single transmembrane domain, we must consider the characteristics of amino acids in transmembrane helices. Transmembrane proteins with multiple alpha-helices that span the membrane can include amino acids with charged, polar side chains as long as these side chains are shielded within the membrane environment.

Without the specific sequences of Helix A, B, C, and D provided in the question, we can infer that the helix with the most hydrophobic or non-polar amino acids is most likely to form a single transmembrane domain. Proteins that span membranes multiple times to form channels will have regions where the polar or charged amino acid residues are present but protected from the hydrophobic interior of the membrane by forming interactions between helices.