Fillingame R H, Peters L K, White L K, Mosher M E, Paule C R
J Bacteriol. 1984 Jun;158(3):1078-83. doi: 10.1128/jb.158.3.1078-1083.1984.
Mutations in the H+-translocating ATPase complex (F1F0) of Escherichia coli have been described in which aspartyl-61 of the omega subunit ( uncE protein) is substituted by either glycine ( uncE105 ) or asparagine ( uncE107 ). Either substitution blocks the H+-translocation activity of the F0 sector of the complex. Here we report a difference in the effects of the two substitutions on the coupled ATPase activity of F1 bound to F0. Wild-type F1 was bound to the F0 of either mutant with affinities comparable to wild-type. The ATPase activity of F1 bound to uncE107 F0 was inhibited by 50%, whereas that bound to uncE105 F0 was not inhibited. Complementation studies with a pBR322-derived plasmid that carried the E gene of the unc operon only indicated that a single mutation in the host strain was responsible for the respective phenotypes. In mutants complemented by the uncE + plasmid, restoration of wild-type biochemical properties was only partial and may be attributed to a mixing of wild-type and mutant omega subunits in a hybrid F0 complex. The activity of membrane-bound F1 was less inhibited in the uncE +/ uncE107 hybrid. Paradoxically, complementation of uncE105 by the uncE + plasmid resulted in substantial inhibition of the activity of membrane-bound F1. The results indicate that a glycine-versus-asparagine substitution for aspartyl-61 must lead to altered conformations of omega and that these differences in conformation are important in the coupling between the F0 and F1 sectors of the complex.
大肠杆菌H⁺转运ATP酶复合体（F1F0）中的突变已被描述，其中ω亚基（uncE蛋白）的天冬氨酸-61被甘氨酸（uncE105）或天冬酰胺（uncE107）取代。任何一种取代都会阻断该复合体F0区段的H⁺转运活性。在此我们报告这两种取代对与F0结合的F1的偶联ATP酶活性的影响存在差异。野生型F1以与野生型相当的亲和力与任一突变体的F0结合。与uncE107 F0结合的F1的ATP酶活性被抑制50%，而与uncE105 F0结合的F1的ATP酶活性未被抑制。仅携带unc操纵子E基因的源自pBR322的质粒进行的互补研究表明，宿主菌株中的单个突变导致了各自的表型。在由uncE⁺质粒互补的突变体中，野生型生化特性的恢复只是部分的，这可能归因于野生型和突变型ω亚基在杂合F0复合体中的混合。在uncE⁺/uncE107杂合体中，膜结合F1的活性受抑制程度较小。矛盾的是，用uncE⁺质粒对uncE105进行互补导致膜结合F1的活性受到显著抑制。结果表明，天冬氨酸-61被甘氨酸或天冬酰胺取代必定导致ω亚基构象改变，并且这些构象差异在该复合体F0和F1区段之间的偶联中很重要。
