https://mmcif.pdb.org/dictionaries/mmcif_pdbx_v50.dic/Items/_pdbx_sifts_xref_db_segments.seq_id_start.html
Data Item _pdbx_sifts_xref_db_segments.seq_id_start
PDBx/mmCIF Data Dictionary Data Item _pdbx_sifts_xref_db_segments.seq_id_start
data itemsiftsxrefsegmentsseq