Vitlin Gruber Anna, Vugman Milena, Azem Abdussalam, Weiss Celeste E
Department of Molecular, Cell and Developmental Biology, University of California, Los Angeles, Los Angeles, CA, United States.
Department of Biochemistry and Molecular Biology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel.
Front Mol Biosci. 2018 Jan 26;5:5. doi: 10.3389/fmolb.2018.00005. eCollection 2018.
Chaperonins are large, essential, oligomers that facilitate protein folding in chloroplasts, mitochondria, and eubacteria. Plant chloroplast chaperonins are comprised of multiple homologous subunits that exhibit unique properties. We previously characterized homogeneous, reconstituted, chloroplast-chaperonin oligomers , each composed of one of three highly homologous beta subunits from . In the current work, we describe alpha-type subunits from the same species and investigate their interaction with β subtypes. Neither alpha subunit was capable of forming higher-order oligomers on its own. When combined with β subunits in the presence of Mg-ATP, only the α2 subunit was able to form stable functional hetero-oligomers, which were capable of refolding denatured protein with native chloroplast co-chaperonins. Since β oligomers were able to oligomerize in the absence of α, we sought conditions under which αβ hetero-oligomers could be produced without contamination of β homo-oligomers. We found that β2 subunits are unable to oligomerize at low temperatures and used this property to obtain homogenous preparations of functional α2β2 hetero-oligomers. The results of this study highlight the importance of reaction conditions such as temperature and concentration for the reconstitution of chloroplast chaperonin oligomers .
伴侣蛋白是大型的、必不可少的寡聚体，可促进叶绿体、线粒体和真细菌中的蛋白质折叠。植物叶绿体伴侣蛋白由具有独特性质的多个同源亚基组成。我们之前对均一的、重组的叶绿体伴侣蛋白寡聚体进行了表征，每个寡聚体由来自……的三个高度同源的β亚基之一组成。在当前的工作中，我们描述了来自同一物种的α型亚基，并研究了它们与β亚型的相互作用。两个α亚基单独都不能形成高阶寡聚体。在Mg-ATP存在的情况下与β亚基结合时，只有α2亚基能够形成稳定的功能性异源寡聚体，这些异源寡聚体能够与天然叶绿体共伴侣蛋白一起使变性蛋白复性。由于β寡聚体能够在没有α的情况下寡聚化，我们寻找能够产生αβ异源寡聚体而不被β同源寡聚体污染的条件。我们发现β2亚基在低温下不能寡聚化，并利用这一特性获得了功能性α2β2异源寡聚体的均一制剂。这项研究的结果突出了温度和浓度等反应条件对叶绿体伴侣蛋白寡聚体重组的重要性。
