Crystallization and preliminary X-ray crystallographic studies of β-transaminase from Mesorhizobium sp. strain LUK

Abstract

β-Transaminase (β-TA) catalyzes the transamination reaction between β-aminocarboxylic acids and keto acids. This enzyme is a particularly suitable candidate for use as a biocatalyst for the asymmetric synthesis of enantiochemically pure β-amino acids for pharmaceutical purposes. The β-TA from Mesorhizobium sp. strain LUK (β-TAMs) belongs to a novel class in that it shows β-transaminase activity with a broad and unique substrate specificity. In this study, β-TAMs was overexpressed in Escherichia coli with an engineered C-terminal His tag. β-TAMs was then purified to homogeneity and crystallized at 293 K. X-ray diffraction data were collected to a resolution of 2.5 Å from a crystal that belonged to the orthorhombic space group C222(1), with unit-cell parameters a = 90.91, b = 192.17, c = 52.75 Å.

Figure 1

Gel-filtration chromatography and SDS–PAGE of β-transaminase from Mesorhizobium sp. strain LUK (β-TAMs).

Figure 2

Crystal of β-transaminase from Mesorhizobium sp. strain LUK (β-TAMs). Crystals were grown in 2 d in the presence of 0.3 M sodium citrate tribasic dihydrate, 0.1 M cadmium chloride hydrate and 0.1 M HEPES pH 7.6. The approximate dimensions of the crystals were 0.1 × 0.4 × 0.1 mm.

Figure 3

A diffraction image (1° oscillation) from a β-TAMs crystal with a 2.5 Å resolution limit.