Fig. 1.

Examples of homomers with different binding site structure. (A) Dimer with single-chain binding sites (SBSs): isopentenyl phosphate kinase from Thermoplasma acidophilum (PDB ID: 3LKK). The ligands (ATP) bind only residues of a single protein chain. (B) Dimer with an multichain binding site (MBS): oxygen-insensitive-NADPH-nitroreductase from Escherichia coli (PDB ID: 1F5V). The ligands (FMN) interact with both chains of the dimer. In both examples, the ligands are shown in red, and the ligand-binding residues are highlighted in yellow.