Cell Signalling and Receptor Mechanisms · USMLE Step 1

Which structural feature is diagnostic of a G-protein–coupled receptor (GPCR)?

  1. A single transmembrane α-helix
  2. Seven transmembrane α-helices
  3. A cytosolic DNA-binding domain
  4. A ligand-gated ion pore composed of multiple subunits
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Correct answer: Seven transmembrane α-helices

GPCRs are defined by their seven transmembrane α-helices, which allow them to transmit extracellular signals via G proteins.

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