Which class of cell surface receptor is characterized by having seven transmembrane domains and is commonly involved in signal transduction via G proteins?

• A. Ligand-gated ion channel
• B. G protein-coupled receptor (GPCR)
• C. Receptor tyrosine kinase
• D. Nuclear hormone receptor

Answer: (B)

Verified step by step guidance

1. Understand the question: The problem asks about a class of cell surface receptors characterized by seven transmembrane domains and their involvement in signal transduction via G proteins.
2. Recall the key features of the receptor types listed: (1) Ligand-gated ion channels are ion channels that open or close in response to ligand binding, but they do not have seven transmembrane domains. (2) G protein-coupled receptors (GPCRs) are known for their seven transmembrane domains and their role in signal transduction via G proteins. (3) Receptor tyrosine kinases (RTKs) are single-pass transmembrane proteins involved in phosphorylation cascades, not G protein signaling. (4) Nuclear hormone receptors are intracellular receptors, not cell surface receptors, and do not have transmembrane domains.
3. Focus on the defining feature: The seven transmembrane domains are a hallmark of GPCRs, which are integral membrane proteins that span the membrane seven times.
4. Connect the function: GPCRs are involved in signal transduction by interacting with G proteins, which transmit signals from extracellular ligands to intracellular pathways.
5. Conclude: Based on the structural and functional characteristics, the correct answer is G protein-coupled receptor (GPCR).