Angov E, Ng T C, Brusilow W S
Department of Biochemistry, Wayne State University School of Medicine, Detroit, Michigan 48201.
J Bacteriol. 1991 Jan;173(1):407-11. doi: 10.1128/jb.173.1.407-411.1991.
During the assembly of the Escherichia coli proton-translocating ATPase, the subunits of F1 interact with F0 to increase the proton permeability of the transmembrane proton channel. We tested the involvement of the delta subunit in this process by partially and completely deleting uncH (delta subunit) from a plasmid carrying the genes for the F0 subunits and delta and testing the effects of those F0 plasmids on the growth of unc+ and unc mutant E. coli strains. We found that the delta subunit was required for inhibition of growth of unc+ cells. We also tested membranes isolated from unc-deleted cells containing F0 plasmids for F1-binding ability. In unc-deleted cells, these plasmids produced F0 in amounts comparable to those found in normal unc+ E. coli cells, while having only small effects on cell growth. These studies demonstrate that the delta subunit plays an important role in opening the F0 proton channel but that it does not serve as a temporary plug of F0 during assembly, as had been previously speculated (S. Pati and W. S. A. Brusilow, J. Biol. Chem. 264:2640-2644, 1989).
在大肠杆菌质子转运ATP酶的组装过程中，F1亚基与F0相互作用，以增加跨膜质子通道的质子通透性。我们通过从携带F0亚基和δ基因的质粒中部分或完全删除uncH（δ亚基），并测试这些F0质粒对unc+和unc突变大肠杆菌菌株生长的影响，来检测δ亚基在这一过程中的作用。我们发现，δ亚基是抑制unc+细胞生长所必需的。我们还测试了从含有F0质粒的unc缺失细胞中分离出的膜的F1结合能力。在unc缺失的细胞中，这些质粒产生的F0量与正常unc+大肠杆菌细胞中的相当，而对细胞生长只有很小的影响。这些研究表明，δ亚基在打开F0质子通道中起重要作用，但它在组装过程中并不像之前推测的那样作为F0的临时堵塞物（S. Pati和W. S. A. Brusilow，《生物化学杂志》264:2640 - 2644，1989）。
