Relaxation of Loaded ESCRT-III Spiral Springs Drives Membrane Deformation.
Bottom Line: We reasoned that Snf7 spirals could function as spiral springs.Furthermore, we observed that the elastic expansion of compressed Snf7 spirals generated an area difference between the two sides of the membrane and thus curvature.This spring-like activity underlies the driving force by which ESCRT-III could mediate membrane deformation and fission.
Affiliation: University of Geneva, Department of Biochemistry, quai Ernest Ansermet 30, 1211 Geneva 4, Switzerland.Show MeSH
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Mentions: These observations prompted the question of how Snf7 patches were formed. Patch nucleation could, for instance, start from a single closed ring, like those seen by EM. It is conceivable that such rings could be prone to break open, thus freeing filament tips that could further grow into a spiral. How would then this initial spiral transform into a patch? A possible scenario consists of a two-step growth mechanism (Figure 3A). First, new spirals are nucleated in the vicinity of existing spirals (termed below spiral nucleation). Rupture of filaments would separate the newly formed spirals from the initial spiral. Second, these spirals would grow independently through the addition of monomers at their filament tips. This scenario accounts for the observed growth dynamics of Snf7 patches: the constant speed of the radial growth of the patches implies that the density of growing filament tips at their rim stays constant. The formation of new spirals generates new tips, maintaining a constant density of growing tips.
Affiliation: University of Geneva, Department of Biochemistry, quai Ernest Ansermet 30, 1211 Geneva 4, Switzerland.