Crystallization and preliminary X-ray analysis of an alanine dehydrogenase from Bacillus megaterium WSH-002

Abstract

Alanine dehydrogenase (L-AlaDH) from Bacillus megaterium WSH-002 catalyses the NAD⁺-dependent interconversion of L-alanine and pyruvate. The enzyme was expressed in Escherichia coli BL21 (DE3) cells and purified with a His6 tag by Ni²⁺-chelating affinity chromatography for X-ray crystallographic analysis. Crystals were grown in a solution consisting of 0.1 M HEPES pH 8.0, 12%(w/v) polyethylene glycol 8000, 8%(v/v) ethylene glycol at a concentration of 15 mg ml⁻¹ purified protein. The crystal diffracted to 2.35 Å resolution and belonged to the trigonal space group R32, with unit-cell parameters a = b = 125.918, c = 144.698 Å.

Keywords: Bacillus megaterium; alanine dehydrogenase.

Figure 1

12% SDS–PAGE analysis of l-AlaDH. Lane M, molecular-mass standards (labelled in kDa); lane 1, purified l-AlaDH protein (42 kDa).

Figure 2

Typical crystals of l-AlaDH protein (with dimensions of ∼200 × 180 × 150 µm).

Figure 3

Typical X-ray diffraction pattern from an l-AlaDH crystal.