FIGURE 8.
Mechanism of NEU1 oligomerization. A, each NEU1 monomer (red circles) has two binding sites on its surface (1 and 2). Monomers bind to each other and form a spiral chain that varies in length. PPCA homodimers (green spheres) compete for binding to NEU1-binding sites 1 or 2 at the ends of the NEU1 chain. B, this results in the formation of PPCA-NEU1 heterodimers and a shorter NEU1 oligomeric chain. C, a structural model of the NEU1 oligomer. Peptide 1 (cyan) of the first molecule interacts with peptide 2 (dark blue) of the second molecule. A free peptide 1 of the second molecule interacts with a free peptide 2 of the third molecule and so on. The distance between the tips of these peptides and the center of the molecule is 25–26 Å, and they are oriented at roughly 70° in relation to each other. D, electron micrograph of purified BV-NEU1 protein confirms the spiral chain structure of the NEU1 oligomers. Scale bar, 7 nm.