Figure 4.
Self-assembly of whole τ and of microtubule binding region. Polymerization of τ4L, 0.04 mg/ml (a), and the association of τ4L with normal brain τ (b) is shown; similar PHF with fuzzy coat were obtained when τ4L was coassembled with τ3L, τ3S, τ3, τ4S, or τ4 (not shown). Acid and heat treatment of τ4L (0.04 mg/ml) inhibited the self-assembly of τ (c). τ constructs τ266–391 and τ297–391 containing the microtubule binding region (0.5 mg/ml) were able to polymerize into short PHF-like filaments, with twists every ≈40 nm (d) or every ≈80 nm (e); similar but several twists longer than those formed from τ4L. Bar represents 50 nm.