Figure 3.

(A) Overlay of Brd2^BD2 (PDB: 3ONI) and Brd3^BD2 (PDB: 3S92) with the crystal structure of the VCB/MZ1/Brd4^BD2 ternary complex (PDB: 5T35) suggests that a VHL/MZ1/Brd3^BD2 ternary complex adopting the equivalent close-packing interaction would likely be less stable due to steric clash with the VHL/MZ1 of a single amino acid within the ZA loop of the bromodomain (Glu344 of Brd3^BD2, which corresponds to Gly386 in Brd4^BD2). (B) Diagram of point mutants generated to explore reciprocal swap of the amino acid at this position. (C) Reciprocal exchange of this single Gly/Glu residue in Brd4^BD2 (i, iii) or Brd3^BD2 (ii, iv) yields a corresponding swap of the kinetic profile in the resulting VHL/MZ1/BD ternary complex SPR sensorgram. For each sensorgram, values shown represent fitted dissociation constants for ternary complex formation (K_D^ternary), dissociative half-life of the ternary complex (t_1/2) (calculated as t_1/2 = ln2/k_off) and cooperativity factor (α) (calculated as α = K_D^binary/K_D^ternary).