Each protein chain is represented using 4 lines:
1: >Protein ID.
2: Amino acid sequence (collected from UniProt).
3: Annotation of PBRs: "P" indicates PBRs while "." indicates non-PBRs
4: Annotations of residues that bind other ligands: "N" indicates nucleic acid-binding residues, "S" indicates small ligand-binding residues, while "." indicates non-binding residues.