Figure 6.

(A) Identification of the minimal ESX peptide that binds DRIP130 in vitro. It is evident that ³⁵S-labeled DRIP130 binds an 8-aa segment of the ESX activation domain (ESX_137–144). (B) Summary of mutational studies. Point mutants of ESX_129–145 were tested for their ability to bind DRIP130. Although the Ala substitution of hydrophilic residues had no effect, those of hydrophobic residues in the putative α-helical region abolished the interaction with DRIP130. The indole structure of Trp-138 seems to be important for the interaction because either substitution with Ala, Phe, or Leu abolished the interaction with DRIP130. (C) Projection of the minimal binding peptide, ESX_137–144, onto a helical wheel.