Crystallization and preliminary X-ray diffraction analysis of a soluble domain of the putative zinc transporter CzrB from Thermus thermophilus

CzrB is a putative zinc transporter from Thermus thermophilus. The protein is proposed to consist of a hexahelical transmembrane domain with a cytosolic extramembranal C‐terminus. The latter 92‐residue fragment may be expressed free and may function independently of the full‐length integral membrane protein. A 6×His‐tagged form of the water‐soluble fragment has been overexpressed in Escherichia coli and diffraction‐quality crystals of the tagged and tag‐free variants have been grown. Preliminary X‐ray analyses of tag‐free fragment crystals with (2.2 Å resolution) and without zinc ions (1.7 Å resolution) reveal that the former has at least two zinc ions bound per monomer.