Matsumori Nobuaki, Yamaji Nahoko, Matsuoka Shigeru, Oishi Tohru, Murata Michio
Department of Chemistry, Graduate School of Science, Osaka University, 1-16 Machikaneyama, Toyonaka, Osaka 560-0043, Japan.
J Am Chem Soc. 2002 Apr 24;124(16):4180-1. doi: 10.1021/ja012026b.
Polyenemacrolides such as amphotericin B (AmB) were thought to assemble together and form an ion channel across plasma membranes. Their antimicrobial activity has been accounted for by this assemblage, whose stability and activity are dependent on sterol constituents of lipid bilayer membranes. The structure of this channel-like assemblage formed in biomembranes has been a target of extensive investigations for a long time. For the first step to this goal, we prepared several AmB dimers with various linkers and tested for their channel-forming activity. Among these, AmB dimers that bore an aminoalkyl-dicarboxylate tether covalently linked between amino groups of AmB showed potent hemolytic activity. Furthermore, K+ influx actions monitored by measuring the pH of the liposome lumen by 31P NMR revealed that the dimers formed the molecular assemblage similar to that of AmB in phospholipid membrane. Judging from changes in 31P NMR spectra, the dimers appeared to induce "all-or-none"-type ion flux across the liposome membrane in the presence of ergosterol, which suggested that the ion channel formed by ergosterol/dimer is similar to that of AmB. With these data in hand, we are now trying to elucidate the structure of the ion-channel complex by making the labeled conjugates of AmB for NMR measurements.
多烯大环内酯类药物如两性霉素B（AmB）被认为会聚集在一起并在质膜上形成一个离子通道。它们的抗菌活性被认为是由这种聚集体导致的，其稳定性和活性取决于脂质双分子层膜中的甾醇成分。生物膜中形成的这种通道样聚集体的结构长期以来一直是广泛研究的目标。为了实现这一目标的第一步，我们制备了几种带有不同连接子的AmB二聚体，并测试了它们的通道形成活性。其中，在AmB的氨基之间共价连接有氨基烷基二羧酸酯链的AmB二聚体表现出强大的溶血活性。此外，通过31P NMR测量脂质体腔的pH值监测K+内流作用，结果表明这些二聚体在磷脂膜中形成了与AmB相似的分子聚集体。从31P NMR光谱的变化判断，在麦角固醇存在的情况下，这些二聚体似乎诱导脂质体膜产生“全或无”型离子通量，这表明麦角固醇/二聚体形成的离子通道与AmB的相似。有了这些数据，我们现在正试图通过制备用于NMR测量的AmB标记共轭物来阐明离子通道复合物的结构。
