From the Department of Chemie and Center for Integrated Protein Science, Technische Universität München, Lichtenbergstrasse 4, 85 748 Garching, Germany
J Biol Chem. 2019 Feb 8;294(6):2121-2132. doi: 10.1074/jbc.REV118.002809. Epub 2018 Oct 31.
Small heat shock proteins (sHsps) are a ubiquitous and ancient family of ATP-independent molecular chaperones. A key characteristic of sHsps is that they exist in ensembles of iso-energetic oligomeric species differing in size. This property arises from a unique mode of assembly involving several parts of the subunits in a flexible manner. Current evidence suggests that smaller oligomers are more active chaperones. Thus, a shift in the equilibrium of the sHsp ensemble allows regulating the chaperone activity. Different mechanisms have been identified that reversibly change the oligomer equilibrium. The promiscuous interaction with non-native proteins generates complexes that can form aggregate-like structures from which native proteins are restored by ATP-dependent chaperones such as Hsp70 family members. In recent years, this basic paradigm has been expanded, and new roles and new cofactors, as well as variations in structure and regulation of sHsps, have emerged.
小分子热休克蛋白（sHsps）是一类普遍存在且古老的 ATP 非依赖型分子伴侣。sHsps 的一个关键特征是，它们以不同大小的同能量寡聚体物种的集合体形式存在。这种特性源于一种独特的组装模式，涉及亚基的几个部分以灵活的方式相互作用。目前的证据表明，较小的寡聚体是更活跃的分子伴侣。因此，sHsp 集合体平衡的改变可以调节分子伴侣的活性。已经确定了不同的机制，可以可逆地改变寡聚体平衡。与非天然蛋白质的混杂相互作用会产生复合物，这些复合物可以形成聚集体样结构，天然蛋白质通过 ATP 依赖性伴侣（如 Hsp70 家族成员）得以恢复。近年来，这一基本模式得到了扩展，出现了新的作用和新的辅助因子，以及 sHsps 的结构和调节的变化。
