Crystallization and preliminary X-ray study of the deaminase AmnE from Pseudomonas sp. AP-3.

The amnE gene from Pseudomonas sp. AP-3 has been verified as encoding a deaminase with 142 amino-acid residues. In order to change the substrate specificity via structure-based protein engineering, the amnE gene, after gene-code optimization, was chemically synthesized and cloned into the expression vector pET-28a. The protein was expressed in Escherichia coli BL21 (DE3) and purified by Ni(2+)-chelating affinity chromatography. Diffraction-quality crystals were obtained using the hanging-drop vapour-diffusion method and diffracted to a resolution of 2.09 Å. The crystals belonged to the orthorhombic space group C2221, with unit-cell parameters a = 63.23, b = 88.93, c = 137.83 Å.