The bacterial HflK-HflC membrane complex is a member of the highly conserved SPFH protein family, which is found throughout all domains of life and includes eukaryotic stomatins, flotillins, and prohibitins. These proteins organize cell membranes and are involved in various processes. However, the exact physiological functions of most bacterial SPFH proteins remain unclear. Here, we report that the HflK-HflC complex in Escherichia coli is required for growth under high aeration. The absence of this complex causes an aerobic growth defect due to a reduced abundance of IspG, a crucial enzyme in the isoprenoid biosynthetic pathway. This reduction leads to lower levels of ubiquinone, reduced respiration, lower ATP levels, and misregulated expression of respiratory genes. The regulation of aerobic respiration by the HflK-HflC complex resembles the mitochondrial respiratory defects caused by prohibitin mutations in mammalian and yeast cells, suggesting a functional commonality between these bacterial and eukaryotic SPFH proteins.

中文翻译：

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SPFH 复合物 HflK-HflC 调节细菌的有氧呼吸

细菌 HflK-HflC 膜复合物是高度保守的 SPFH 蛋白家族的成员，该蛋白家族存在于生命的各个领域，包括真核生物的气孔素、flotillins 和抑制素。这些蛋白质组织细胞膜并参与各种过程。然而，大多数细菌 SPFH 蛋白的确切生理功能仍不清楚。在这里，我们报道了大肠杆菌中的 HflK-HflC 复合物是高通气条件下生长所必需的。该复合物的缺失会导致需氧生长缺陷，因为 IspG 丰度减少，而 IspG 是类异戊二烯生物合成途径中的关键酶。这种减少导致泛醌水平降低、呼吸减少、ATP 水平降低以及呼吸基因表达失调。 HflK-HflC 复合物对有氧呼吸的调节类似于哺乳动物和酵母细胞中抑制素突变引起的线粒体呼吸缺陷，表明这些细菌和真核 SPFH 蛋白之间存在功能共性。