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 cytosolic face of the membrane. The loop on the cytosolic side between helices 5 and 6 is usually substantially longer than the others.

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 cytosolic face of the membrane. The loop on the cytosolic side between helices 5 and 6 is usually substantially longer than the others.

Use this description to answer the following question.

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 cytosolic face of the membrane. The loop on the cytosolic side between helices 5 and 6 is usually substantially longer than the others.


The coupled G protein most likely interacts with this receptor



A. along the exterior margin.
B. along the interior margin.
C. at the loop between H5 and H6.
D. at the NH3 end.
E. at the COO- end.


Answer: C