Crystallization and preliminary X-ray diffraction analysis of the magnesium transporter CorA

The full-length integral membrane protein CorA from Thermotoga maritima (TmCorA(1-351)) has been expressed in Escherichia coli and purified without membrane isolation. TmCorA(1-351) crystallized in the monoclinic space group C2, with unit-cell parameters a = 214.25, b = 86.30, c = 181.53 angstrom, beta = 112.23 degrees. Native crystals diffracted to 3.7 angstrom using synchrotron radiation, but selenomethionine-substituted crystals rarely diffracted to better than 5.0 angstrom. All full-length protein crystals were highly mosaic and produced anisotropic diffraction patterns. To aid in crystallographic phasing, soluble domain constructs were screened and the periplasmic domain of CorA from Archaeoglobus fulgidus (AfCorA(1-263)) was crystallized in the hexagonal space group P6(1)22, with unit-cell parameters a = b = 101.17, c = 142.87 angstrom. Native and SeMet-substituted AfCorA(1-263) crystals diffracted to similar to 3.0 angstrom using synchrotron radiation.