What best describes GPCR structure?

What best describes GPCR structure?

• A. 4 transmembrane segments; extracellular domain binds ligands; cytosolic tail interacts with kinases
• B. 7 transmembrane regions; extracellular ligand-binding, cytosolic domain couples to G-protein
• C. Single-pass receptor; binds ligand on extracellular side
• D. Nuclear receptor with DNA-binding domain

Answer: (B)

GPCRs are built with seven transmembrane segments that weave through the cell membrane. The N-terminus sits outside the cell to bind ligands, while the cytosolic surface on the inside of the membrane provides a docking site for G proteins. When a ligand binds, the seven-helix bundle changes shape in a way that creates or reveals this cytosolic G-protein coupling interface, allowing the G protein to exchange GDP for GTP and transmit the signal inside the cell. This combination of a seven-pass transmembrane structure with extracellular ligand binding and intracellular G-protein coupling is the hallmark described here. Other descriptions don’t fit GPCRs as well. A implies four transmembrane segments and kinase interactions, which aligns more with non-GPCR receptors. C describes a single-pass receptor, and D refers to a nuclear receptor that binds DNA, neither of which match GPCR architecture.

GPCRs are built with seven transmembrane segments that weave through the cell membrane. The N-terminus sits outside the cell to bind ligands, while the cytosolic surface on the inside of the membrane provides a docking site for G proteins. When a ligand binds, the seven-helix bundle changes shape in a way that creates or reveals this cytosolic G-protein coupling interface, allowing the G protein to exchange GDP for GTP and transmit the signal inside the cell. This combination of a seven-pass transmembrane structure with extracellular ligand binding and intracellular G-protein coupling is the hallmark described here.

Other descriptions don’t fit GPCRs as well. A implies four transmembrane segments and kinase interactions, which aligns more with non-GPCR receptors. C describes a single-pass receptor, and D refers to a nuclear receptor that binds DNA, neither of which match GPCR architecture.