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首页> 外文期刊>Biochemistry >Structure of Ala24/Asp61->Asp24/Asn61 substituted subunit c of escherichia coli ATP synthase:implications for the mechanism of proton transport and rotary movement in the F_0 complex
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Structure of Ala24/Asp61->Asp24/Asn61 substituted subunit c of escherichia coli ATP synthase:implications for the mechanism of proton transport and rotary movement in the F_0 complex

机译：大肠杆菌ATP合酶的Ala24 / Asp61-> Asp24 / Asn61取代的亚基c的结构：对F_0络合物中质子运输和旋转运动的机理的启示

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The structure of the A24D/D61N substituted subunit c of Escherichia coli ATP synthase,in which the essential carboxylate has been switched from residue 61 of the second transmembrane helic (TMH) to residue 24 of the first TMH,has been determinded by heteronuclear multidimensional NMR in a monophasic chloroform/methanol/water(4:4:1)solvent mixture.As in the case of the wild-type protein,A24D/D61N substituted subunit c forms a haripin of two extended #alpha#-helices(residues 5-39 and 46-78),with residues 40-45 forming a connecting loop at the center of the protein.The structure was determined at pH5,where Asp24 is fully protonated.The relative orientation of the two extended helices in the A24D/D61N structure is different from that inthe protonated form of the wild-type protein,also determined at pH5.The C-terminal helix is rotated by 150deg relative to the wild-type structure,and the N-terminal helix is rotated such that the essential Asp24 carboxyl gorup packs on the same side of the molecule as Asp61 in the wild-type protein.The changes in helix-helic orientation lead to a structure that is quite similar to that of the deprotonated form of wild-type subunit c,determined at pH8.When a decameric ring of c subunits was modeled from the new structure,the Asp24 carboxyl group ws found to pack in a carity at the interface between two subunits that is similar to the acvity in which Asp61 of the wild-type protein is predicted to pack.The interacting faces of the packed subunits in this model are also similar to those in the wild-type model.The results provide further evidence that sunbunit c is likely to fold in at least two conformational states differing most notably in the orientation of the C-terminal helix.Based upon the structure,a mechainistic model is discurssed that indicates how the wild-type and A24D/D61N subunits could utilize similar helical movements during H~+ transport-coupled rotation of the decameric c ring.
机译：大肠杆菌ATP合酶的A24D / D61N取代的亚基c的结构已通过异核多维NMR确定，其中必需的羧酸盐已从第二个跨膜螺旋（TMH）的残基61转换为第一个TMH的残基24。在单相氯仿/甲醇/水（4：4：1）溶剂混合物中。与野生型蛋白质一样，A24D / D61N取代的亚基c形成两个扩展的＃alpha＃-螺旋（残基5- 39和46-78），残基40-45在蛋白质中心形成连接环。在pH5下确定结构，其中Asp24完全质子化.A24D / D61N结构中两个延伸的螺旋的相对方向不同于质子化形式的野生型蛋白质，质子化形式也是在pH5下测定的。C末端螺旋相对于野生型结构旋转了150度，N末端螺旋旋转使得必需的Asp24羧基在m的同一侧包装在野生型蛋白中的分子为Asp61。螺旋-螺旋方向的变化导致其结构与野生型c亚基的去质子化形式非常相似，该结构在pH8下测定。根据新的结构建模，发现Asp24羧基在两个亚基之间的界面上堆积成龋齿，这与预计野生型蛋白的Asp61会堆积的活性相似。该模型还与野生型模型相似。结果提供了进一步的证据，证明日光单位c可能会折叠成至少两个构象状态，最明显的是C末端螺旋的方向不同。讨论了一种链模型，该模型表明野生型和A24D / D61N亚基在十聚体c环的H〜+运输耦合旋转过程中如何利用相似的螺旋运动。

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