AbstractThe small subunit of ribonucleotide reductase from Escherichia coli has been crystallized in two new crystal forms. The form most suitable for X-ray analysis belongs to the orthorhombic space group P212121. It,has the cell dimensions 74.3 Å, 85.5 Å, 115.7 Å and diffracts to about 2.1 Å resolution. The asymmetric unit most probably contains one dimer. Absorption spectra of single crystals confirm that the crystals contain a binuclear iron center. Crystals of the iron-depleted apoenzyme have also been obtained
