Use this description to answer the following questions.
A major group of G protein-coupled receptors contains seven transmembrane α helices. The amino end of the protein lies at the exterior of the plasma membrane. Loops of amino acids connect the helices either at the exterior face or on the cytosol face of the membrane. The loop on the cytosol side between helices 5 and 6 is usually substantially longer than the others.
-The coupled G protein most likely interacts with this receptor
A) at the NH₃ end.
B) at the COO- end.
C) along the exterior margin.
D) along the interior margin.
E) at the loop between H5 and H6.

Question

Quizplus · Accepted Answer

The longer cytosolic loop between helices 5 and 6 is a characteristic feature of this major group of G protein-coupled receptors, suggesting that this loop is involved in G protein interaction. Therefore, the coupled G protein most likely interacts with the receptor at the loop between helices 5 and 6.

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