Ligand/small molecule

In the PDB,  small molecules (low molecular weight organic compounds that are not part of polymers) are frequently associated with biomacromolecules.

Any substance that binds specifically and reversibly to a biomacromolecule to form a larger complex and alters its activity or function is called a ligand. In the PDB, drugs, metals, and small molecules are also called ligands. 

Here we show examples of ligands bound to protein (figure 19) and DNA (figure 20).

An example of a ligand  binding to cytochrome c-553

Figure 19 An example of a ligand  binding to cytochrome c-553 (in green, yellow, blue) is prosthetic group Haem containing an iron ion.



An example of a ligand binding to DNA

Figure 20 An example of a ligand binding to DNA: drug, bleomycin a2.

Information about ligand interactions can be found in Motif and Sites Services link on the PDBe website at PDBeMotif and about ligands at PDBeChem