Specific sequences in the N-terminal domain of human small heat-shock protein HSPB6 dictate preferential hetero-oligomerization with the orthologue HSPB1
Specific sequences in the N-terminal domain of human small heat-shock protein HSPB6 dictate preferential hetero-oligomerization with the orthologue HSPB1
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DOI：
10.1074/jbc.m116.773515
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发表时间：
2017-06-16
影响因子：
4.8
通讯作者：
Weeks, Stephen D.
中科院分区：
文献类型：
--
作者：
Heirbaut, Michelle;Lermyte, Frederik;Weeks, Stephen D.
小分子热休克蛋白（Small heat-shock proteins，sHSPs）是一类保守的分子伴侣，在细胞蛋白质稳定中起重要作用。虽然sHSP的特征在于它们的小单体重量，但它们通常组装成大小和形状都不同但主要由二聚体结构单元组成的大的多分散低聚物。这些组件可以包括不同的sHSP直向同源物，产生额外的复杂性，可能会影响伴侣活性。然而，这种杂寡聚体的结构和功能特性知之甚少。我们开始对人热休克蛋白家族B（小）成员1（HSPB 1）和HSPB 6之间的异源寡聚体形成感兴趣，这两种蛋白都在骨骼肌中高度表达。当在体外混合时，这两种sHSP形成仅由异二聚体组成的多分散低聚物阵列，表明在单体水平上确定的优先缔合。以前，我们已经表明，sHSP的N-末端结构域（NTDs），这具有高度的内在障碍，是必不可少的偏见的形成。在这里，我们采用迭代删除映射来阐明如何热休克蛋白B6的NTD影响其优先协会与热休克蛋白B1，并表明该地区有多个RLFDQXFG是必要的亚基之间的交换寡聚体。其次，类似于该基序下游20个残基的位点决定了所得异源寡聚体的大小。第三，HSPB 6特有的区域决定了异二聚体的优先形成。总之，热休克蛋白B6的无序NTD有助于调节异源寡聚复合物的大小和稳定性，表明末端sHSP区域定义了这些蛋白质的组装特性。
Small heat-shock proteins (sHSPs) are a conserved group of molecular chaperones with important roles in cellular proteostasis. Although sHSPs are characterized by their small monomeric weight, they typically assemble into large polydisperse oligomers that vary in both size and shape but are principally composed of dimeric building blocks. These assemblies can include different sHSP orthologues, creating additional complexity that may affect chaperone activity. However, the structural and functional properties of such hetero-oligomers are poorly understood. We became interested in hetero-oligomer formation between human heat-shock protein family B (small) member 1 (HSPB1) and HSPB6, which are both highly expressed in skeletal muscle. When mixed in vitro, these two sHSPs form a polydisperse oligomer array composed solely of heterodimers, suggesting preferential association that is determined at the monomer level. Previously, we have shown that the sHSP N-terminal domains (NTDs), which have a high degree of intrinsic disorder, are essential for the biased formation. Here we employed iterative deletion mapping to elucidate how the NTD of HSPB6 influences its preferential association with HSPB1 and show that this region has multiple RLFDQXFG is necessary for subunit exchange among oligomers. Second, a site similar to 20 residues downstream of this motif determines the size of the resultant hetero-oligomers. Third, a region unique to HSPB6 dictates the preferential formation of heterodimers. In conclusion, the disordered NTD of HSPB6 helps regulate the size and stability of hetero-oligomeric complexes, indicating that terminal sHSP regions define the assembly properties of these proteins.