Category entity_poly Category entity_poly 
Category Description
Data items in the ENTITY_POLY category record details about the
polymer, such as the type of the polymer, the number of
monomers, and whether it has non-standard features.
Local Description For each biomolecule identified in the Molecule Names category, give the amino acid or nucleic acid sequence using standard one-letter nomenclature.All residues in the crystal, including residues missing due to disorder or lack of electron density, should be included in the sequence.
Also enter the chain identifiers from your PDB format coordinate file corresponding to each entity. A single entity may have multiple chain_id's if there are multiple molecules of the same sequence in the asymmetric unit.
The one-letter code sequence derived from your coordinates is displayed by Pre-Deposition Data Format Check. You may copy this result into the "One-letter sequence code" item below and edit as necessary.
Category Examples 
Example 1:
Example 1 - based on PDB entry 5HVP and laboratory records for the
structure corresponding to PDB entry 5HVP
loop_
_entity_poly.entity_id
_entity_poly.type
_entity_poly.nstd_chirality
_entity_poly.nstd_linkage
_entity_poly.nstd_monomer
_entity_poly.type_details
1 polypeptide(L) no no no .
Key Category Items 
Items in Category entity_poly