Magnan Breanna, Dumont Thomas, Rashid Suad, LaPointe Paul, Spyracopoulos Leo
Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada.
Department of Cell Biology, University of Alberta, Edmonton, Alberta, Canada.
J Biol Chem. 2025 May 21;301(6):110262. doi: 10.1016/j.jbc.2025.110262.
Heat shock protein 90 (Hsp90) is a vital molecular chaperone that is essential for activating a diverse array of regulatory proteins through an ATP-dependent clamping cycle. The Hsp90 clamping cycle is driven by large-amplitude conformational changes within the N-terminal ATPase domain, including the release of an autoinhibitory N-terminal β-strap followed by a less well-characterized ATP gate rearrangement involving N-terminal helix 1. Here, we employed a combination of F NMR spectroscopy, molecular dynamics simulations, and ATPase assays to examine the effects of targeted β-strap and helix 1 mutations. Our findings reveal that targeted disruption of helix 1 packing against the ATPase domain accelerates clamp closure, symmetrically enhancing ATP hydrolysis for both subunits of the Hsp90 dimer, whereas activation by the Aha1 (activator of Hsp90 activity 1) cochaperone is disrupted. Decreasing the energy barrier associated with helix 1 release is a key step in modulating the energy landscape that governs the dynamics of the Hsp90 clamping cycle.
热休克蛋白90（Hsp90）是一种至关重要的分子伴侣，通过ATP依赖的钳夹循环激活多种调节蛋白。Hsp90钳夹循环由N端ATP酶结构域内的大幅度构象变化驱动，包括释放自抑制性N端β带，随后是涉及N端螺旋1的特征不太明确的ATP门重排。在此，我们结合F NMR光谱、分子动力学模拟和ATP酶分析来研究靶向β带和螺旋1突变的影响。我们的研究结果表明，靶向破坏螺旋1与ATP酶结构域的堆积会加速钳夹闭合，对称地增强Hsp90二聚体两个亚基的ATP水解，而Aha1（Hsp90活性激活剂1）共伴侣的激活作用则被破坏。降低与螺旋1释放相关的能垒是调节控制Hsp90钳夹循环动力学的能量景观的关键步骤。
