Cell Signalling and Receptor Mechanisms · USMLE Step 1

Which of these describes a common feature of enzyme-linked receptors (like RTKs)?

  1. Seven membrane-spanning transmembrane alpha-helical domains
  2. An intrinsic or associated intracellular catalytic (enzymatic) domain
  3. Formation of a ligand-gated transmembrane ion pore on binding
  4. Perpetual irreversible activation once the ligand is bound
Show answer and explanation

Correct answer: An intrinsic or associated intracellular catalytic (enzymatic) domain

Enzyme-linked receptors carry or recruit enzymatic activity — often a kinase — in their intracellular domain; ligand binding activates this catalytic function to initiate downstream signaling.

Difficulty: Medium Question 15 of 22

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