Oeemig Jesper S, Ollila O H Samuli, Iwaï Hideo
Research Program in Structural Biology and Biophysics, Institute of Biotechnology, University of Helsinki, Helsinki, Finland.
VIB Center for Structural Biology, Vlaams Instituut voor Biotechnologie (VIB), Vrije Universiteit Brussel, Brussels, Belgium.
PeerJ. 2018 Aug 27;6:e5412. doi: 10.7717/peerj.5412. eCollection 2018.
The TonB protein plays an essential role in the energy transduction system to drive active transport across the outer membrane (OM) using the proton-motive force of the cytoplasmic membrane of Gram-negative bacteria. The C-terminal domain (CTD) of TonB protein is known to interact with the conserved TonB box motif of TonB-dependent OM transporters, which likely induces structural changes in the OM transporters. Several distinct conformations of differently dissected CTDs of TonB have been previously reported. Here we determined the solution NMR structure of a 96-residue fragment of TonB (TonB-96). The structure shows a monomeric structure with the flexible C-terminal region (residues 338-342), different from the NMR structure of TonB (TonB-137). The extended and flexible C-terminal residues are confirmed by N relaxation analysis and molecular dynamics simulation. We created models for the TonB-96/TonB box interaction and propose that the internal fluctuations of TonB-96 makes it more accessible for the interactions with the TonB box and possibly plays a role in disrupting the plug domain of the TonB-dependent OM transporters.
托纳B蛋白在能量转导系统中起着至关重要的作用，它利用革兰氏阴性菌细胞质膜的质子动力来驱动跨外膜（OM）的主动运输。已知托纳B蛋白的C端结构域（CTD）与托纳B依赖性外膜转运蛋白的保守托纳B框基序相互作用，这可能会诱导外膜转运蛋白的结构变化。此前已报道了托纳B不同切割的CTD的几种不同构象。在此，我们确定了托纳B的一个96个残基片段（托纳B-96）的溶液核磁共振结构。该结构显示为具有柔性C端区域（残基338-342）的单体结构，与托纳B（托纳B-137）的核磁共振结构不同。通过N弛豫分析和分子动力学模拟证实了C端残基的延伸和柔性。我们构建了托纳B-96/托纳B框相互作用的模型，并提出托纳B-96的内部波动使其更易于与托纳B框相互作用，并且可能在破坏托纳B依赖性外膜转运蛋白的塞子结构域中发挥作用。
