Adenosine monophosphate (AMP)–activated protein kinase (AMPK) regulates metabolism in response to the cellular energy states. Under energy stress, AMP stabilizes the active AMPK conformation, in which the kinase activation loop (AL) is protected from protein phosphatases, thus keeping the AL in its active, phosphorylated state. At low AMP:ATP (adenosine triphosphate) ratios, ATP inhibits AMPK by increasing AL dynamics and accessibility. We developed conformation-specific antibodies to trap ATP-bound AMPK in a fully inactive, dynamic state and determined its structure at 3.5-angstrom resolution using cryo–electron microscopy. A 180° rotation and 100-angstrom displacement of the kinase domain fully exposes the AL. On the basis of the structure and supporting biophysical data, we propose a multistep mechanism explaining how adenine nucleotides and pharmacological agonists modulate AMPK activity by altering AL phosphorylation and accessibility.

腺苷单磷酸 (AMP) 活化蛋白激酶 (AMPK) 响应细胞能量状态调节代谢。在能量压力下，AMP 稳定活跃的 AMPK 构象，其中激酶激活环 (AL) 受到蛋白质磷酸酶的保护，从而使 AL 保持其活跃的磷酸化状态。在低 AMP:ATP（三磷酸腺苷）比率下，ATP 通过增加 AL 动力学和可及性来抑制 AMPK。我们开发了构象特异性抗体，以完全无活性的动态状态捕获 ATP 结合的 AMPK，并使用冷冻电子显微镜以 3.5 埃的分辨率确定其结构。激酶结构域的 180° 旋转和 100 埃位移完全暴露了 AL。在结构和支撑生物物理数据的基础上，