Cloning, expression, purification, crystallization and X-ray crystallographic analysis of Rv3168 from Mycobacterium tuberculosis H37Rv

Tuberculosis is a widespread and deadly infectious disease, with one third of the human population already being infected. Aminoglycoside antibiotics have become less effective in recent years owing to antibiotic resistance, which arises primarily through enzymatic modification of the antibiotics. The gene product Rv3168, a putative aminoglycoside phosphotransferase (APH), from Myco-bacterium tuberculosis was crystallized using the sitting-drop vapour-diffusion method in the presence of 0.2 M calcium acetate, 0.1 M Tris-HCl pH 7.0 and 20% PEG 3000 at 295 K. X-ray diffraction data were collected to a maximum resolution of 1.67 Å on a synchrotron beamline. The crystal belonged to space group P2₁2₁2₁, with unit-cell parameters a = 56.74, b = 62.37, c = 103.61 Å. With one molecule per asymmetric unit, the crystal volume per unit protein weight (V_M) is 2.91 ų Da^-1. The structure was solved by the single-wavelength anomalous dispersion method and refinement of the selenomethionine structure is in progress.