Hydrogen sulfide is a signaling molecule that regulates essential processes in plants, such as autophagy. In Arabidopsis (Arabidopsis thaliana), hydrogen sulfide negatively regulates autophagy independently of reactive oxygen species via an unknown mechanism. Comparative and quantitative proteomic analysis was used to detect abscisic acid-triggered persulfidation that reveals a main role in the control of autophagy mediated by the autophagy-related (ATG) Cys protease AtATG4a. This protease undergoes specific persulfidation of Cys170 that is a part of the characteristic catalytic Cys-His-Asp triad of Cys proteases. Regulation of the ATG4 activity by persulfidation was tested in a heterologous assay using the Chlamydomonas reinhardtii CrATG8 protein as a substrate. Sulfide significantly and reversibly inactivates AtATG4a. The biological significance of the reversible inhibition of the ATG4 by sulfide is supported by the results obtained in Arabidopsis leaves under basal and autophagy-activating conditions. A significant increase in the overall ATG4 proteolytic activity in Arabidopsis was detected under nitrogen starvation and osmotic stress and can be inhibited by sulfide. Therefore, the data strongly suggest that the negative regulation of autophagy by sulfide is mediated by specific persulfidation of the ATG4 protease.

硫化氢是一种信号分子，可调节植物中的基本过程，例如自噬。在拟南芥 ( Arabidopsis thaliana ) 中，硫化氢通过未知机制独立于活性氧对自噬进行负调节。比较和定量蛋白质组学分析用于检测脱落酸引发的过硫化，揭示了自噬相关 (ATG) 半胱氨酸蛋白酶 AtATG4a 介导的自噬控制中的主要作用。这种蛋白酶经历了 Cys170 的特异性过硫化作用，Cys170 是 Cys 蛋白酶的特征催化性 Cys-His-Asp 三联体的一部分。在使用莱茵衣藻的异源测定中测试了通过过硫化作用对 ATG4 活性的调节CrATG8 蛋白作为底物。硫化物显着且可逆地使 AtATG4a 失活。硫化物对 ATG4 的可逆抑制的生物学意义得到了拟南芥叶片在基础和自噬激活条件下获得的结果的支持。在氮饥饿和渗透胁迫下检测到拟南芥中整体 ATG4 蛋白水解活性显着增加，并且可以被硫化物抑制。因此，数据强烈表明硫化物对自噬的负调节是由 ATG4 蛋白酶的特异性过硫化介导的。