The electrostatic surface potential covering a range from -4 kT/e (red/acidic) to +4 kT/e (blue/basic) is mapped onto the Sir4 H‑BRCT structure to highlight the basic patch on the H‑BRCT surface. Sir4 H‑BRCT is shown in two orientations rotated by 180° and selected residues are labeled. Superpositions of Sir4 H‑BRCT-Esc1pS1450 (grey cartoon, peptide as sticks in atom colors), Sir4 H‑BRCT-Ty5pS1095 (blue cartoon, peptide as sticks in atom colors), and Sir4 H‑BRCT-Ubp10pT123 (green cartoon, peptide as sticks in atom colors) peptide complex structures reveal the highly similar conformation of peptide binders. Esc1pS1450, Ty5pS1095, and Ubp10pT123 peptides used for co-crystallization are indicated with residues modeled in the structures in bold and residues that contribute most binding to Sir4 H‑BRCT boxed. 