A 124-residue N-terminal fragment corresponding to the DNA-binding domain of the Saccharomyces cerevisae cell-cycle transcription factor MBP-1 has been expressed with a hexahistidine affinity tag in E. coli and purified to apparent homogeneity. Crystals have been grown using PEG 3350 as precipitant which diffract x-rays to greater than 2.6 Angstrom resolution. The space group is tetragonal, P4(3)2(1)2 or P4(1)2(1)2 with unit cell dimensions a = b = 42.2 Angstrom. c = 123.2 Angstrom and a monomer in the asymmetric unit. (C) 1997 Wiley-Liss, Inc.