DNA binding protein II binds non-specifically to double-stranded DNA in prokaryotes inducing the formation of bead-like structure similar to those formed by histories in eukaryotes. The 3Å structure of this protein has been determined and a DNA binding model through two symmetry-related flexible arms is proposed. The molecule has also a site similar to putative DNA binding site of gene regulatory proteins, whose implications are discussed. A mechanism by which the molecule induces condensed structure to DNA is proposed. [J. Cryst. Soc. Jpn. 26, 325 (1984) ] .
