The structure of BtuB with bound colicin E3 R-domain implies a translocon
The structure of BtuB with bound colicin E3 R-domain implies a translocon
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DOI：
10.1038/nsb997
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发表时间：
2003-11-01
期刊：
影响因子：
--
通讯作者：
Cramer, WA
中科院分区：
文献类型：
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作者：
Kurisu, G;Zakharov, SD;Cramer, WA
大肠杆菌素E3的细胞输入是由大肠杆菌外膜钴胺转运蛋白（BtuB）启动的。大肠杆菌素E3的135个残基100埃的线圈受体结合域（R135）与BtuB形成1:1的配合物，其结构分辨率为2.75埃。R135与BtuB细胞外表面的结合（DeltaGdegrees = -12 kcal mol(-1)）是由27个R135的残基介导的。R135 BtuB复合物的形成导致R135 N-末端和c -末端的展开，这被认为对colicin t结构域的展开很重要。在BtuB的软木和桶状结构域中会发生小的构象变化，但不足以形成易位通道。通道的缺失和R135的外周结合表明，BtuB可以结合colicin，而卷曲的线圈将colicin传递给邻近的外膜蛋白进行易位，从而形成colicin易位子。从大肠杆菌素E3阻塞OmpF通道的角度推断该转运体为OmpF。
Cellular import of colicin E3 is initiated by the Escherichia coli outer membrane cobalamin transporter, BtuB. The 135-residue 100-Angstrom coiled-coil receptor-binding domain (R135) of colicin E3 forms a 1: 1 complex with BtuB whose structure at a resolution of 2.75 Angstrom is reported. Binding of R135 to the BtuB extracellular surface (DeltaGdegrees = -12 kcal mol(-1)) is mediated by 27 residues of R135 near the coiled-coil apex. Formation of the R135 BtuB complex results in unfolding of R135 N- and C-terminal ends, inferred to be important for unfolding of the colicin T-domain. Small conformational changes occur in the BtuB cork and barrel domains but are insufficient to form a translocation channel. The absence of a channel and the peripheral binding of R135 imply that BtuB serves to bind the colicin, and that the coiled-coil delivers the colicin to a neighboring outer membrane protein for translocation, thus forming a colicin translocon. The translocator was concluded to be OmpF from the occlusion of OmpF channels by colicin E3.