Superposition of Sir4 (orange) and Dbf4 (PDB 3QBZ, cyan) H‑BRCT domains highlighting the structural conservation of the Sir4 phospho-epitope binding region in Dbf4. The only change is the Arg1066 (Sir4 H‑BRCT) replacement to Lys200 (Dbf4 H‑BRCT), highlighted by an arrow, while all other residues are conserved. 