Two crystal forms of ModE, the molybdate-dependent transcriptional regulator from Escherichia coli

The molybdenum-responsive ModE regulatory protein from Escherichia coli has been purified and used in crystallization trials. Two crystal forms have b een observed. Form I is tetragonal, P4(1)2(1)2 (or enantiomorph), with a = b = 72.3, c = 246.2 Angstrom and diffracts to medium resolution. Form II is orthorhombic, P2(1)2(1)2, with a = 82.8, b = 127.9, c = 63.0 Angstrom and diffraction has been observed beyond 2.8 Angstrom resolution. Structural an alysis, in combination with ongoing biochemical characterization, will assi st the elucidation of the structure-activity relationship in regulating the uptake of molybdate in bacteria.