A mechanism of proton translocation by F1F0 ATP synthases suggested by double mutants of the a subunit.
A mechanism of proton translocation by F1F0 ATP synthases suggested by double mutants of the a subunit.
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DOI：
10.1016/s0021-9258(18)43822-7
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发表时间：
1994-12
期刊：
影响因子：
--
通讯作者：
Steven B. VikS;B. Antonio
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文献类型：
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作者：
Steven B. VikS;B. Antonio
大肠杆菌F1F0 ATP合酶的a亚基中的三个氨基酸残基是质子转运所必需的：Arg210、Glu219和His245。在这项研究中，必需的谷氨酸已被重新定位到252位，保留了功能。已知Gln252可以被Glu取代而没有显著影响。为了测试Q252E是否会在Glu219不存在的情况下起作用，设计了“定点第二位点抑制剂”实验。饱和诱变残基Glu219，并分离出14个不同的氨基酸取代，其中5个允许在琥珀酸基本培养基上生长在37 ℃：天冬氨酸，赖氨酸，甘氨酸，丙氨酸，丝氨酸。这些结果表明，Q252E可以提供必要的羧基通常由Glu219提供，但严格的要求被放置在位置219上的残基。我们解释这些结果意味着Q252E必须占据，至少部分，正常的位置Glu219。我们提出了一种新的机制，质子转运的F1F0 ATP酶，其中包括一个旋转的低聚体的c亚基，其中Asp61的两个c亚基同时与Glu219和Arg210的a亚基相互作用。这种机制可以适用于线粒体和钠驱动的细菌ATP酶。
Three amino acid residues in the a subunit of the Escherichia coli F1F0 ATP synthase are essential for proton translocation: Arg210, Glu219, and His245. In this study, the essential glutamic acid has been relocated to position 252 with retention of function. It had been known that Gln252 can be replaced by Glu without significant effect. To test whether Q252E would function in the absence of Glu219, a “site-directed second-site suppressor” experiment was designed. Saturation mutagenesis was applied to residue Glu219, and 14 different amino acid substitutions were isolated, five of which permitted growth on succinate minimal medium at 37 degrees C: Asp, Lys, Gly, Ala, and Ser. These results indicate that Q252E can provide the essential carboxyl group normally provided by Glu219, but that strict requirements are placed on the residue at position 219. We interpret these results to mean that the Q252E must occupy, at least partially, the normal position of Glu219. We present a novel mechanism of proton translocation by F1F0 ATP synthases that includes a rotating oligomer of c subunits, in which the Asp61 of two c subunits simultaneously interact with Glu219 and Arg210 of the a subunit. This mechanism can be adapted for both mitochondrial and sodium-driven bacterial ATP synthases.