Overexpression, purification, crystallization and structure determination of AspB, a putative aspartate aminotransferase fromMycobacterium tuberculosis
A recombinant version of a putative aspartate aminotransferase, AspB (encoded by the ORF Rv3565), fromMycobacterium tuberculosis(Mtb) was overexpressed inM. smegmatisand purified to homogeneity using liquid chromatography. Crystals of AspB were grown in a condition consisting of 0.2 Mammonium phosphate monobasic, 0.1 Mcalcium chloride dihydrate employing the hanging-drop vapour-diffusion method at 298 K. The crystals diffracted to a limit of 2.50 Å resolution and belonged to the orthorhombic space groupP212121, with unit-cell parametersa= 93.27,b= 98.19,c= 198.70 Å. The structure of AspB was solved by the molecular-replacement method using a putative aminotransferase fromSilicibacter pomeroyi(PDB entry 3h14) as the search model. The template shares 46% amino-acid sequence identity withMtbAspB. The crystal asymmetric unit contains four AspB molecules (theMrof each is 42 035 Da).