Chanturiya A, Chernomordik L V, Zimmerberg J
Laboratory of Cellular and Molecular Biophysics, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
Proc Natl Acad Sci U S A. 1997 Dec 23;94(26):14423-8. doi: 10.1073/pnas.94.26.14423.
For the act of membrane fusion, there are two competing, mutually exclusive molecular models that differ in the structure of the initial pore, the pathway for ionic continuity between formerly separated volumes. Because biological "fusion pores" can be as small as ionic channels or gap junctions, one model posits a proteinaceous initial fusion pore. Because biological fusion pore conductance varies widely, another model proposes a lipidic initial pore. We have found pore opening and flickering during the fusion of protein-free phospholipid vesicles with planar phospholipid bilayers. Fusion pore formation appears to follow the coalescence of contacting monolayers to create a zone of hemifusion where continuity between the two adherent membranes is lipidic, but not aqueous. Hypotonic stress, causing tension in the vesicle membrane, promotes complete fusion. Pores closed soon after opening (flickering), and the distribution of fusion pore conductance appears similar to the distribution of initial fusion pores in biological fusion. Because small flickering pores can form in the absence of protein, the existence of small pores in biological fusion cannot be an argument in support of models based on proteinaceous pores. Rather, these results support the model of a lipidic fusion pore developing within a hemifused contact site.
对于膜融合过程，存在两种相互竞争、相互排斥的分子模型，它们在初始孔的结构以及先前分离的区域之间离子连续性的途径方面存在差异。由于生物“融合孔”可能小至离子通道或间隙连接，一种模型假定存在蛋白质构成的初始融合孔。由于生物融合孔的电导变化很大，另一种模型则提出存在脂质初始孔。我们发现在无蛋白的磷脂囊泡与平面磷脂双层融合过程中存在孔的开放和闪烁现象。融合孔的形成似乎是通过接触单层的合并来创建一个半融合区域，在该区域中两个附着膜之间的连续性是脂质的而非水性的。低渗应激会在囊泡膜中产生张力，从而促进完全融合。孔在开放后很快关闭（闪烁），并且融合孔电导的分布似乎与生物融合中初始融合孔的分布相似。由于在没有蛋白质的情况下可以形成小的闪烁孔，因此生物融合中存在小孔不能作为支持基于蛋白质孔的模型的论据。相反，这些结果支持了在半融合接触位点内形成脂质融合孔的模型。
