10.17615/QWA3-E576
Lentz, Barry R.
University of North Carolina at Chapel Hill
Seeing Is Believing: The Stalk Intermediate
The University of North Carolina at Chapel Hill University Libraries
2006
Article
en
In Copyright
Membrane biophysicists have sought the molecular nature of biomembrane fusion for more than 30 years. In this time, two conflicting hypotheses have evolved to explain very different observations. One, based on electrophysiological measurements on patch-clamped cells (1), is the proteinacious pore hypothesis. This model, popular among neurobiologists, contends that the initial fusion pore consists of a single proteinacious channel that later opens into a full fusion pore due to dissipation of the initial protein pore components into lipid bilayer. Recent mutational studies of the trans-membrane domain of the synaptic fusion protein syntaxin claim to support this hypothesis and propose that several syntaxin trans-membrane domain's may form the initial pore (2). The alternative hypothesis is the lipidic pore hypothesis. It contends that the fusion pore derives from nonlamellar lipid structures and proceeds through an initial partially fused structure in which lipids mix although aqueous compartments do not. The partially fused state is termed hemifusion. A large number of observations offer support for this view for viral, exocytotic, and model systems (3–8). Despite the preponderance of evidence for the lipidic pore hypothesis, no one has until now actually observed in a biological system a lipidic pore or one of the presumed lipidic intermediates thought to precede the lipidic pore. An article in this issue of the Biophysical Journal (9) dramatically alters this situation.