Quel Natália G, Fernando de C Rodrigues Luiz, Aragão Annelize Z B, Pinheiro Glaucia M S, Camacho Rafael P, Souto Denio E P, Kubota Lauro T, Barbosa Leandro R S, Ramos Carlos H I
Institute of Chemistry, University of Campinas UNICAMP, Campinas SP, 13083-970 Brazil; National Institute of Science & Technology of Structural Biology and Bioimage (INCTBEB), Brazil.
Institute of Physics, University of São Paulo, São Paulo SP, 05508-090 Brazil.
Biochimie. 2021 Aug;187:131-143. doi: 10.1016/j.biochi.2021.05.012. Epub 2021 May 31.
SGTs (small glutamine-rich TPR-containing proteins) are dimeric proteins that belong to the class of co-chaperones characterized by the presence of TPR domains (containing tetratricopeptide repeats). Human (SGTA) and yeast (Sgt2) SGTs are characterized by three distinct domains: an N-terminal dimerization domain, a central TPR-domain important for binding to other proteins (chaperones included) and a C-terminal domain involved in hydrophobic interactions. Both these SGTs are involved in the cellular PQC (protein quality control) system, as they interact with chaperones and have functions that aid stress recovery. However, there are differences between them, such as structural features and binding specificities, that could be better understood if other orthologous proteins were studied. Therefore, we produced and characterized a putative SGT protein, designated AaSGT, from the mosquito Aedes aegypti, which is a vector of several diseases, such as dengue and Zika. The protein was produced as a folded dimer which was stable up to 40 °C and was capable of binding to AaHsp90 and fully protecting a model protein, α-synuclein, from aggregation. The conformation of AaSGT was investigated by biophysical tools and small angle X-ray scattering, which showed that the protein had an elongated conformation and that its C-terminal domain was mainly disordered. The results with a C-terminal deletion mutant supported these observations. Altogether, these results are consistent with those from other functional SGT proteins and add to the understanding of the PQC system in Aedes aegypti, an important aim that may help to develop inhibitory strategies against this vector of neglected diseases.
富含谷氨酰胺的小TPR结构域蛋白（SGTs）是二聚体蛋白，属于共伴侣蛋白类别，其特征是存在TPR结构域（包含四肽重复序列）。人类的SGTA和酵母的Sgt2具有三个不同的结构域：一个N端二聚化结构域、一个对与其他蛋白（包括伴侣蛋白）结合很重要的中央TPR结构域，以及一个参与疏水相互作用的C端结构域。这两种SGT都参与细胞的蛋白质质量控制系统（PQC），因为它们与伴侣蛋白相互作用并具有有助于应激恢复的功能。然而，它们之间存在差异，例如结构特征和结合特异性，如果研究其他直系同源蛋白，可能会更好地理解这些差异。因此，我们从埃及伊蚊（几种疾病的传播媒介，如登革热和寨卡病毒）中制备并鉴定了一种假定的SGT蛋白，命名为AaSGT。该蛋白以折叠二聚体形式产生，在高达40°C时稳定，能够与AaHsp90结合，并能完全保护模型蛋白α-突触核蛋白不发生聚集。通过生物物理工具和小角X射线散射研究了AaSGT的构象，结果表明该蛋白具有拉长的构象，其C端结构域主要是无序的。C端缺失突变体的结果支持了这些观察结果。总之，这些结果与其他功能性SGT蛋白的结果一致，并有助于增进对埃及伊蚊PQC系统的理解，这一重要目标可能有助于开发针对这种被忽视疾病传播媒介的抑制策略。
