Department of Biochemistry and Molecular Biology, Graduate School of Science and Engineering, Saitama University, Saitama 338-8570, Japan.
J Biochem. 2021 Apr 18;169(3):351-361. doi: 10.1093/jb/mvaa108.
In contrast to Escherichia coli, cyanobacteria have multiple GroELs, the bacterial homologues of chaperonin/Hsp60. We have shown that cyanobacterial GroELs are mutually distinct and different from E. coli GroEL with which the paradigm for chaperonin structure/function has been established. However, little is known about regulation of cyanobacterial GroELs. This study investigated effect of pH (varied from 7.0 to 8.5) on chaperone activity of GroEL1 and GroEL2 from the cyanobacterium Synechococcus elongatus PCC7942 and E. coli GroEL. GroEL1 and GroEL2 showed pH dependency in suppression of aggregation of heat-denatured malate dehydrogenase, lactate dehydrogenase and citrate synthase. They exhibited higher anti-aggregation activity at more alkaline pHs. Escherichia coli GroEL showed a similar pH-dependence in suppressing aggregation of heat-denatured lactate dehydrogenase. No pH dependence was observed in all the GroELs when urea-denatured lactate dehydrogenase was used for anti-aggregation assay, suggesting that the pH-dependence is related to some denatured structures. There was no significant influence of pH on the chaperone activity of all the GroELs to promote refolding of heat-denatured malate dehydrogenase. It is known that pH in cyanobacterial cytoplasm increases by one pH unit following a shift from darkness to light, suggesting that the pH-change modulates chaperone activity of cyanobacterial GroEL1 and GroEL2.
与大肠杆菌不同，蓝藻有多个 GroEL，这是伴侣蛋白/热休克蛋白 60 的细菌同源物。我们已经表明，蓝藻 GroEL 是相互不同的，与已建立伴侣蛋白结构/功能范例的大肠杆菌 GroEL 不同。然而，关于蓝藻 GroEL 的调控知之甚少。本研究调查了 pH 值（从 7.0 到 8.5 变化）对 Synechococcus elongatus PCC7942 蓝藻和大肠杆菌 GroEL 的 GroEL1 和 GroEL2 伴侣活性的影响。GroEL1 和 GroEL2 在抑制热变性苹果酸脱氢酶、乳酸脱氢酶和柠檬酸合酶聚集方面表现出 pH 依赖性。它们在更碱性的 pH 值下表现出更高的抗聚集活性。大肠杆菌 GroEL 对热变性乳酸脱氢酶的聚集抑制也表现出类似的 pH 依赖性。当使用脲变性的乳酸脱氢酶进行抗聚集测定时，所有 GroEL 都没有观察到 pH 依赖性，这表明 pH 依赖性与某些变性结构有关。所有 GroEL 对热变性苹果酸脱氢酶的折叠促进的伴侣活性没有显著的 pH 影响。已知蓝藻细胞质中的 pH 值在从黑暗到光照的转变后会增加一个 pH 单位，这表明 pH 值的变化可以调节蓝藻 GroEL1 和 GroEL2 的伴侣活性。
