Barranger-Mathys M, Cafiso D S
Department of Chemistry, University of Virginia, Charlottesville 22901.
Biophys J. 1994 Jul;67(1):172-6. doi: 10.1016/S0006-3495(94)80466-7.
Alamethicin is a 20-amino-acid peptide that produces a voltage-dependent conductance in membranes. We investigated the state of aggregation of alamethicin in egg phosphatidylcholine and dioleoylphosphatidylcholine membranes by examining the EPR spectra obtained from an active analog of this peptide that is spin-labeled at its C-terminus. The dependence of both the linewidth and signal intensity as a function of peptide concentration exhibit exchange broadening as the peptide concentration is increased; however, the exchange rates are linear with peptide concentration as is expected for the simple diffusion of monomers. In addition, the spin-exchange rates obtained from the linebroadening are consistent with collisional rates that are predicted from free Brownian diffusion. The results provide strong evidence that in the absence of a membrane potential, alamethicin is largely monomeric in these membranes.
阿拉霉素是一种由20个氨基酸组成的肽，可在膜中产生电压依赖性电导。我们通过检查从该肽的活性类似物（其C端进行了自旋标记）获得的电子顺磁共振（EPR）光谱，研究了阿拉霉素在鸡蛋磷脂酰胆碱和二油酰磷脂酰胆碱膜中的聚集状态。随着肽浓度的增加，线宽和信号强度对肽浓度的依赖性均表现出交换加宽；然而，交换速率与肽浓度呈线性关系，这与单体的简单扩散预期一致。此外，从线宽加宽获得的自旋交换速率与自由布朗扩散预测的碰撞速率一致。结果提供了有力证据，表明在没有膜电位的情况下，阿拉霉素在这些膜中主要以单体形式存在。
