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 been observed. Form I is tetragonal, P41212 (or enantiomorph), with a = b = 72.3, c = 246.2 A and diffracts to medium resolution. Form II is orthorhombic, P21212, with a = 82.8, b = 127.9, c = 64.0 A and diffraction has been observed beyond 2.8 A resolution. Structural analysis, in combination with ongoing biochemical characterization, will assist the elucidation of the structure-activity relationship in regulating the uptake of molybdate in bacteria.