Starostin A V, Butan R, Borisenko V, James D A, Wenschuh H, Sansom M S, Woolley G A
Department of Chemistry, University of Toronto, 80 St. George Street, Toronto M5S 3H6, Canada.
Biochemistry. 1999 May 11;38(19):6144-50. doi: 10.1021/bi9826355.
The peptide alamethicin self-assembles to form helix bundle ion channels in membranes. Previous macroscopic measurements have shown that these channels are mildly cation-selective. Models indicate that a source of cation selectivity is a zone of partial negative charge toward the C-terminal end of the peptide. We synthesized an alamethicin derivative with a lysine in this zone (replacing the glutamine at position 18 in the sequence). Microscopic (single-channel) measurements demonstrate that dimeric alamethicin-lysine18 (alm-K18) forms mildly anion-selective channels under conditions where channels formed by the parent peptide are cation-selective. Long-range electrostatic interactions can explain the inversion of ion selectivity and the conductance properties of alamethicin channels.
肽类抗生素短杆菌肽A在膜中自组装形成螺旋束离子通道。先前的宏观测量表明，这些通道具有轻度的阳离子选择性。模型表明，阳离子选择性的一个来源是肽C末端的部分负电荷区域。我们在该区域合成了一种含有赖氨酸的短杆菌肽A衍生物（取代序列中第18位的谷氨酰胺）。微观（单通道）测量表明，在亲本肽形成的通道具有阳离子选择性的条件下，二聚体短杆菌肽A-赖氨酸18（alm-K18）形成轻度阴离子选择性通道。长程静电相互作用可以解释短杆菌肽A通道离子选择性的反转和电导特性。
