FIGURE 10:

The Hec1 tail as a phosphorylation-controlled rheostat for tuning NDC80-MT binding. (A) Increasing numbers of Hec1 tail phosphorylations tune NDC80-MT affinity by reducing the energy of NDC80-MT binding, while NDC80 binding cooperativity is unchanged. Symbols are as in Figure 1B; note that the MT is rotated 180° relative to the schematic in Figure 1B. (B) Proposed dual mechanism to explain rheostasis of NDC80 (blue) binding to polymerized tubulin (gray). The site-specific lock-and-key binding by the globular head is assisted by the conformationally unstable protein extension, which additively integrates the output from multiple phosphorylation events (purple circles) regardless of their exact location.