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.

中文翻译：

---

pH介导的对蓝细菌和大肠杆菌伴侣蛋白GroELs的抗聚集活性的控制

与大肠杆菌相反，蓝细菌具有多种GroEL，即伴侣蛋白/ Hsp60的细菌同源物。我们已经表明，蓝藻GroELs是彼此不同的，并且不同于建立伴侣蛋白结构/功能范例的大肠杆菌GroELs 。然而，关于蓝藻GroELs的调控知之甚少。这项研究调查了pH值（从7.0到8.5）对蓝藻Synechococcus elongatus PCC7942和大肠杆菌的GroEL1和GroEL2分子伴侣活性的影响。GroEL。GroEL1和GroEL2在抑制热变性的苹果酸脱氢酶，乳酸脱氢酶和柠檬酸合酶的聚集中显示出pH依赖性。它们在更多的碱性pH值下表现出更高的抗聚集活性。大肠杆菌GroEL在抑制热变性乳酸脱氢酶的聚集方面显示出类似的pH依赖性。当尿素变性的乳酸脱氢酶用于抗聚集测定时，在所有GroEL中均未观察到pH依赖性，这表明pH依赖性与某些变性结构有关。pH对所有GroEL的分子伴侣活性促进热变性的苹果酸脱氢酶的重折叠没有显着影响。众所周知，从黑暗转移到光亮之后，蓝细菌细胞质中的pH值增加一个pH单位，这表明pH值的变化调节了蓝细菌GroEL1和GroEL2的分子伴侣活性。