BAR scaffolds drive membrane fission by crowding disordered domains

Wilton T. Snead; Wade F. Zeno; Grace Kago; Ryan W. Perkins; J Blair Richter; Chi Zhao; Eileen M. Lafer; Jeanne C. Stachowiak

Amphiphysin is composed of an N-terminal, amphipathic helix BAR (N-BAR) domain, followed by an intrinsically disordered protein (IDP) domain of approximately 383 amino acids in humans, and a C-terminal SH3 domain (Miele et al., 2004; Owen et al., 2004; Owen et al., 1998; Peter et al., 2004) (Fig. 1A) . To compare membrane bending by fulllength amphiphysin (Amph-FL) to the N-BAR domain alone, we first examined the effects of each protein on giant unilamellar vesicles (GUVs). These experiments revealed that both the N-BAR domain and Amph-FL drove potent membrane bending, forming mobile, diffraction-limited tubules that extended from the GUV surface (Fig. S1A , Movies S1 and S2). These GUVs often collapsed or broke apart into smaller tubules and fragments (Movies S3 and S4), suggesting that lipid tubule formation may not have been the endpoint of the membrane remodeling process.