Fig. 1.

Structure and hierarchy of α-helical SAFs. (A) Two heterodimer-directing peptides (SAF-p1, SAF-p2a) assemble to form a sticky-ended unit that associates further to form coiled-coil fibrils, which are hexagonally packed within the SAFs. Each peptide has two differently charged regions: In both cases, the N and C terminal halves are predominantly basic and acidic, respectively, and are colored blue and pink accordingly. (B and C) Fibrils associate laterally to form fibers (B) that display striations (C) after staining with heavy-metal salts and visualization by TEM. Scale bars, 2 μm (B) and 50 nm (C).