Authors state that the biological unit is a tetramer protein plus a 32-mer DNA molecule, as indicated as pentamer in remark 350. Please refer to remark 999 for more details on the sequences specificity of this crystal structure.
THE SEQUENCE OF THE CRYSTALLIZED DNA IS A 32-MER OLIGONUCLEOTIDE WITH SEQUENCE ...THE SEQUENCE OF THE CRYSTALLIZED DNA IS A 32-MER OLIGONUCLEOTIDE WITH SEQUENCE TTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTT. ONLY 9 RESIDUES WERE MODELED IN THE COORDINATES OF THE ASYMMETRIC UNIT. ACCORDING TO THE AUTHORS, THE 32-MER DNA BINDS A TETRAMER THAT INCLUDE FOUR MONOMERS OF FOUR ASYMMETRIC UNITS; THE STWHY2-DNA BINDING IS NOT SEQUENCE SPECIFIC THUS EACH TETRAMERIC PROTEIN BINDS A 32-MER DNA IN DIFFERENT SEQUENCE REGISTERS; AS A RESULT ONLY THREE OF THE FOUR DNA-BINDING SITES OF EACH TETRAMER WOULD BE PHYSICALLY OCCUPIED BY THE DNA.