Figure 5.

The Δ280^K and 301^L, but not 279^K or 305^N, mutations impair the functions of tau in vitro. (A) Tau binding to MTs. Binding curves were generated by fitting data using nonlinear regression with the standard binding equation: (bound tau) = B_max × (free tau)/[K_d+(free tau)]. The B_max and K_d values are listed in Table 2. Symbols: ■, normal; ▵, 279^K; ∗, Δ280^K; ⋄, 301^L; ●, 305^N. (B) Tau-promoted MT assembly. Bovine tubulin monomers (35 μM) were mixed at 4°C with 15 μM recombinant tau in RA buffer supplemented with 1 mM GTP. Samples were warmed to 37°C, and MT assembly was monitored by optical density at 350 nm (A₃₅₀). A representative result is shown and the lag times, initiation rates, and A₃₅₀ max values (n = 6) are summarized in Table 2. Symbols are as in A; ♦ indicates no added tau.