Wang Hsiu-Jung, Kuan Yun-Erh, Ho Meng-Ru, Chang Chung-I
Institute of Biological Chemistry, Academia Sinica, Taipei, 11529, Taiwan.
Institute of Biochemical Sciences, College of Life Science, National Taiwan University, Taipei, 10617, Taiwan.
Nat Commun. 2025 Mar 5;16(1):2212. doi: 10.1038/s41467-025-57482-6.
Lon is a conserved AAA+ (ATPases associated with diverse cellular activities) proteolytic machine that plays a key regulatory role in cells under proteotoxic stress. Lon-mediated proteolysis can be stimulated by either the unfolded or specific protein substrates accumulated under stress conditions. However, the molecular basis for this substrate-controlled proteolysis remains unclear. Here, we have found that the heat shock protein LarA, a recently discovered Lon substrate and allosteric activator, binds to the N-terminal domain (NTD) of Lon. The crystal structure of the LarA-NTD complex shows that LarA binds to a highly conserved groove in the NTD through the terminal aromatic residue of its C-terminal degron. Crystallographic and biochemical evidence further reveals that this binding exposes the hydrophobic core of LarA, which can bind a leucine residue and promote local protein unfolding. These results define the mechanistic role of the NTD in regulating Lon-mediated proteolysis in response to varying cellular conditions.
Lon是一种保守的AAA+（与多种细胞活动相关的ATP酶）蛋白水解机器，在蛋白毒性应激下的细胞中发挥关键的调节作用。Lon介导的蛋白水解可被应激条件下积累的未折叠或特定蛋白质底物所刺激。然而，这种底物控制的蛋白水解的分子基础仍不清楚。在这里，我们发现热休克蛋白LarA，一种最近发现的Lon底物和变构激活剂，与Lon的N端结构域（NTD）结合。LarA-NTD复合物的晶体结构表明，LarA通过其C端降解子的末端芳香族残基与NTD中一个高度保守的凹槽结合。晶体学和生化证据进一步表明，这种结合暴露了LarA的疏水核心，该核心可以结合一个亮氨酸残基并促进局部蛋白质展开。这些结果确定了NTD在响应不同细胞条件下调节Lon介导的蛋白水解中的机制作用。
