Crystallization and X-ray diffraction analysis of the sensor domain of the HemAT aerotactic receptor.

HemAT is a 432-amino-acid protein with two structural domains identified from Bacillus subtilis. It is responsible for sensing oxygen and delivering the signal to the downstream signal transduction cascade through a two-component system [Hou et al. (2000), Nature (London), 403, 540-544]. The consequence of such events is to change the flagellar movement and alter the swimming behavior of bacteria. To elucidate the molecular mechanism of oxygen sensing, the sensor domain of HemAT from B. subtilis was cloned, expressed and crystallized. Multiple-wavelength anomalous dispersion (MAD) data were collected from the intrinsic anomalous scatterer, iron, using synchrotron radiation. Three-wavelength iron MAD data sets were collected to 2.8 A resolution. The native data set was collected to 2.15 A resolution. Initial crystallographic analysis revealed the crystals to belong to space group P2(1)2(1)2(1), with unit-cell parameters a = 50.00, b = 80.12, c = 85.95 A. There is one dimer in the asymmetric unit, with 40% solvent content. Structure determination using MAD methods and model building are currently under way.