![]() ![]() By analogy to fusion, it has been, however, suggested that they operate through a similar stalk intermediate ( Kozlovsky and Kozlov, 2003). However, in all these fission reactions, it is not known whether the different machineries mediate fission on the basis on the same principle, mostly because physical understanding of how fission is mediated is lacking. Small GTPases (Sar1, Arf1) involved in the initiation of the coat proteins (COPs)-dependent Golgi trafficking have also been recently implicated in the fission reaction of the COPs ( Fromme et al., 2007). In the case of fission, different machineries mediate the separation of two compartments depending on the cellular context: dynamin during endocytosis endosomal sorting complex in retrograde transport-III (ESCRT-III) in multivesicular body biogenesis, cytokinesis, and viral budding ( Hurley and Hanson, 2010). The stalk intermediate is a structure where the cytosolic leaflets of the two membrane compartments are fused into one, whereas the lumenal leaflets are still separated. The general principle of the SNAREs mechanism is that the energy spent in the assembly of the SNARE complex overcomes the energy barrier to fusion by generating a hemifusion intermediate, also called the “stalk intermediate” ( Kozlovsky and Kozlov, 2002). ![]() In many of the various fusion events in cells, a single type of machinery, the SNAREs, mediate the collapse of membranes. Membrane fission is an essential step in membrane traffic, as it separates membrane cargoes from donor compartments. ![]()
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