Question 11

Question:

A researcher studying a rare genetic disease finds that patients with the disease are missing both copies of a gene. This gene encodes a protein containing seven-helix transmembrane domains. Which type of protein is this most likely to be?

Correct Answer: A.  G protein-coupled receptor

The G-protein coupled receptors (A) all contain seven transmembrane segments. Importantly, all metabotropic receptors span the cell membrane and contain cytoplasmic and extracellular faces.

The other molecules mentioned are all membrane-bound proteins, but they do not contain seven transmembrane helices.

The basic structure of MHC Class II (B) receptors, and T-cell (D) and Toll Like Receptors (E) should be familiar. They contain regions for ligand docking, but do not span the host cell’s membane multiple times.

The Na/K ATPase (C) is a bidrectional active ion passing channel , that contains much more structural complexity than any of the other choices.