.cif to .pdb
PyMol
File > Export Structure > Export Molecule > Save > change "save as type"
SeqIO.parse
from Bio import SeqIO
records = SeqIO.parse("input_file.cif", "cif-atom")
SeqIO.write(records, "output_file.pdb", "pdb-atom")
RCSB maxit
maxit -i file.cif -o 2