Crystal structure of a 92-residue C-terminal fragment of TonB from Escherichia coli reveals significant conformational changes compared to structures of smaller TonB fragments
Crystal structure of a 92-residue C-terminal fragment of TonB from Escherichia coli reveals significant conformational changes compared to structures of smaller TonB fragments
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DOI：
10.1074/jbc.m411155200
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发表时间：
2005-01-28
影响因子：
4.8
通讯作者：
Welte, W
中科院分区：
文献类型：
--
作者：
Ködding, J;Killig, F;Welte, W
大肠杆菌外膜对铁载体和维生素 B 的摄取受到由多个外膜受体和内膜蛋白质复合物组成的主动转运系统的影响。它们之间的联系是 TonB，一种与细胞质膜相关的蛋白质，它形成一个大的周质结构域，能够与多个外膜受体相互作用，例如FhuA、FecA 和 FepA 代表铁载体，BtuB 代表维生素 B-12。跨外膜的主动转运由内膜的化学渗透梯度驱动，并由 TonB 蛋白介导。 TonB 的受体结合结构域似乎是由类似 100 个残基的高度保守的 C 端氨基酸序列形成的。先前已确定了分别由 85 个 (TonB-85) 和 77 个 (TonB-77) 个氨基酸残基组成的两个 C 端 TonB 片段的晶体结构 (Chang, C.、Mooser, A.、Pluckthun, A. 和 Wlodawer, A. (2001) J. Biol. Chem. 276,27535-27540 和 Koedding, J., Howard, S. P.、Kaufmann, L.、Polzer, P.、Lustig, A. 和 Welte, W. (2004) J. Biol. 279, 9978-9986)。在这两种情况下，TonB 片段在溶液中形成二聚体，并结晶为由通过交换 β 发夹和 C 端 β 链而彼此紧密接合的单体组成的二聚体。 Here we present the crystal structure of a 92-residue fragment of TonB (TonB-92), which is monomeric in solution.该结构以 1.13 埃分辨率测定，显示出与其他已知的 TonB 结构相比，分子间相互作用显着减少的二聚体，特别是缺乏 β-发夹交换。
Uptake of siderophores and vitamin B,, through the outer membrane of Escherichia coli is effected by an active transport system consisting of several outer membrane receptors and a protein complex of the inner membrane. The link between these is TonB, a protein associated with the cytoplasmic membrane, which forms a large periplasmic domain capable of interacting with several outer membrane receptors, e.g. FhuA, FecA, and FepA for siderophores and BtuB for vitamin B-12. The active transport across the outer membrane is driven by the chemiosmotic gradient of the inner membrane and is mediated by the TonB protein. The receptor-binding domain of TonB appears to be formed by a highly conserved C-terminal amino acid sequence of similar to100 residues. Crystal structures of two C-terminal TonB fragments composed of 85 (TonB-85) and 77 (TonB-77) amino acid residues, respectively, have been previously determined (Chang, C., Mooser, A., Pluckthun, A., and Wlodawer, A. (2001) J. Biol. Chem. 276,27535-27540 and Koedding, J., Howard, S. P., Kaufmann, L., Polzer, P., Lustig, A., and Welte, W. (2004) J. Biol. Chem. 279, 9978-9986). In both cases the TonB fragments form dimers in solution and crystallize as dimers consisting of monomers tightly engaged with one another by the exchange of a beta-hairpin and a C-terminal beta-strand. Here we present the crystal structure of a 92-residue fragment of TonB (TonB-92), which is monomeric in solution. The structure, determined at 1.13-Angstrom resolution, shows a dimer with considerably reduced intermolecular interaction compared with the other known TonB structures, in particular lacking the beta-hairpin exchange.