Schmitt J D, Sansom M S, Kerr I D, Lunt G G, Eisenthal R
School of Biology and Biochemistry, University of Bath, U.K.
Biochemistry. 1997 Feb 4;36(5):1115-22. doi: 10.1021/bi962168w.
The synthesis and single-channel characterization of two redox-active C-terminal derivatives of alamethicin are herein described. The reduced [Fe(II)] forms of ferrocenoyl-alamethicin (Fc-ALM) and 1'-carboxyferrocenoyl-alamethicin (cFc-ALM) are shown to form voltage-dependent ion channels at cis positive potentials in planar lipid bilayers (PLB) with conductance properties similar to those of alamethicin. In situ oxidation of Fc-ALM [to Fe(III)] in the PLB apparatus causes a time-dependent elimination of channel openings, which can be restored by an increase in the transbilayer potential. In contrast, oxidation of cFc-ALM leads to the formation of shorter-lived channels. Pretreatment of the ferrocenoyl peptides with oxidizing agent alters their single-channel properties in a qualitatively similar manner, establishing that the changes in channel properties in the presence of oxidizing agents are due specifically to ferrocenoyl oxidation. We suggest that the redox sensitivity of these ferrocene-containing ion channels may be governed by a combination of the following factors: (1) changes in hydrophobicity; (2) alteration of peptide molecular dipole; and (3) alterations in tendencies toward self-association. However, oxidation induced changes in peptide conformation cannot be ruled out. Our results provide evidence that it is possible to engineer channel-forming peptides that respond to specific changes in the chemical environment.
本文描述了两种氧化还原活性的阿拉霉素C末端衍生物的合成及单通道特性。二茂铁酰基-阿拉霉素（Fc-ALM）和1'-羧基二茂铁酰基-阿拉霉素（cFc-ALM）的还原态[Fe(II)]在平面脂质双层（PLB）中，于顺式正电位下可形成电压依赖性离子通道，其电导特性与阿拉霉素相似。在PLB装置中，Fc-ALM原位氧化为[Fe(III)]会导致通道开放随时间逐渐消失，而跨膜电位的增加可使其恢复。相反，cFc-ALM的氧化会导致形成寿命较短的通道。用氧化剂预处理二茂铁酰基肽会以定性相似的方式改变其单通道特性，这表明在氧化剂存在下通道特性的变化具体是由于二茂铁酰基氧化所致。我们认为，这些含二茂铁离子通道的氧化还原敏感性可能受以下因素共同影响：（1）疏水性变化；（2）肽分子偶极的改变；（3）自缔合倾向的改变。然而，不能排除氧化诱导肽构象变化的可能性。我们的结果提供了证据，表明有可能设计出对化学环境的特定变化有响应的通道形成肽。
