This is activator-binding domain (ABD1) found in Gal11/med15 proteins. Structural analysis indicate that it binds to the central activator domain (cAD) of Gcn4. Mutations in Gal11-ABD1 W196 residue abolishes the binding to Gcn4 cAD [1].

1: The acidic transcription activator Gcn4 binds the mediator subunit Gal11/Med15 using a simple protein interface forming a fuzzy complex. Brzovic PS, Heikaus CC, Kisselev L, Vernon R, Herbig E, Pacheco D, Warfield L, Littlefield P, Baker D, Klevit RE, Hahn S; Mol Cell. 2011;44:942-953. PMID:22195967