Department of Biochemistry, School of Biology, Moscow State University, Russian Federation.
Arch Biochem Biophys. 2011 Sep 1;513(1):1-9. doi: 10.1016/j.abb.2011.06.014. Epub 2011 Jul 13.
Interaction of human Bag3 with small heat shock proteins HspB6, HspB8 and its K141E mutant was analyzed by different biochemical methods. The data of size-exclusion chromatography indicate that the wild type HspB8 forms tight complexes with Bag3. K141E mutant of HspB8 and especially HspB6 weaker interact with Bag3. The data of chemical crosslinking and analytical ultracentrifugation indicate that in vitro the stoichiometry of complexes formed by HspB8 and Bag3 is variable and is dependent on concentration of protein partners. Interaction of Bag3 and HspB8 is accompanied by increase of thermal stability measured by intrinsic tryptophan fluorescence and increased resistance to limited chymotrypsinolysis. The data of size-exclusion chromatography, analytical ultracentrifugation and limited proteolysis indicate that Bag3 belongs to the group of intrinsically disordered proteins. It is supposed that having unordered structure Bag3 might weakly interact with different small heat shock proteins which recognize unfolded proteins and this interaction is especially strong with intrinsically disordered HspB8. The complexes formed by Bag3 and HspB8 might have variable stoichiometry and can participate in different processes including clearing of the cell from improperly folded proteins.
采用不同的生化方法分析了人 Bag3 与小分子热休克蛋白 HspB6、HspB8 及其 K141E 突变体的相互作用。凝胶排阻色谱的数据表明，野生型 HspB8 与 Bag3 形成紧密的复合物。HspB8 的 K141E 突变体和 HspB6 与 Bag3 的相互作用较弱。化学交联和分析超速离心的数据表明，在体外，由 HspB8 和 Bag3 形成的复合物的化学计量是可变的，并且依赖于蛋白质伴侣的浓度。Bag3 与 HspB8 的相互作用伴随着由内源色氨酸荧光测量的热稳定性的增加和对有限胰蛋白酶水解的抗性的增加。凝胶排阻色谱、分析超速离心和有限蛋白水解的数据表明，Bag3 属于无规卷曲蛋白组。据推测，具有无规卷曲结构的 Bag3 可能与识别未折叠蛋白质的不同小分子热休克蛋白弱相互作用，与无规卷曲的 HspB8 的相互作用尤其强烈。由 Bag3 和 HspB8 形成的复合物可能具有可变的化学计量，并且可以参与不同的过程，包括从错误折叠的蛋白质中清除细胞。
