Department of Chemistry, University of Konstanz, Konstanz 78457, Germany.
Protein Sci. 2010 Apr;19(4):625-30. doi: 10.1002/pro.345.
TonB from Escherichia coli and its homologues are critical for the uptake of siderophores through the outer membrane of Gram-negative bacteria using chemiosmotic energy. When different models for the mechanism of TonB mediated energy transfer from the inner to the outer membrane are discussed, one of the key questions is whether TonB spans the periplasm. In this article, we use long range distance measurements by spin-label pulsed EPR (Double Electron-Electron Resonance, DEER) and CD spectroscopy to show that the proline-rich segment of TonB exists in a PPII-like conformation. The result implies that the proline-rich segment of TonB possesses a length of more than 15 nm, sufficient to span the periplasm of Gram-negative bacteria.
大肠杆菌中的 TonB 及其同源物对于利用化学渗透能量通过革兰氏阴性菌的外膜摄取铁载体至关重要。当讨论 TonB 介导的能量从内膜到外膜转移的不同机制模型时，关键问题之一是 TonB 是否跨越周质空间。在本文中，我们使用长程距离测量自旋标记脉冲电子顺磁共振（Double Electron-Electron Resonance，DEER）和 CD 光谱来表明 TonB 的脯氨酸丰富片段存在于 PPII 样构象中。该结果表明 TonB 的脯氨酸丰富片段具有超过 15nm 的长度，足以跨越革兰氏阴性菌的周质空间。
