Figure 4.

Tubulin binding sites in R2 and R3. Diffusion times are plotted of tau-tubulin complexes formed by tau constructs containing either four or three microtubule binding repeats. The solid and dashed lines denote the upper and lower boundaries, respectively, of 1:1 tau-tubulin complexes as described in the text and in Fig. 3. The four-repeat series, in which all constructs contain both IR_1/2–R2 and IR_2/3–R3, bind with a >1:1 stoichiometry and significant heterogeneity. In the three-repeat series, only P123 and P132 bind with >1:1 stoichiometry. Constructs lacking either IR_1/2–R2 (P134) or IR_2/3–R3 (P124) have smaller median diffusion times, reflecting smaller complexes and lower stoichiometry. To see this figure in color, go online.