Crystallization and preliminary X-ray analysis of an alkaline serine protease from Nesterenkonia sp.

A novel calcium-independent serine protease from an alkaliphilic bacterium, Nesterenkonia sp. AL20, has been purified and crystallized at 296 K using sodium formate as the main precipitant. This enzyme is optimally active at pH 10, exhibits high stability towards autolytic digestion and its stability is not affected by the presence of EDTA or detergents. The triangular prism-shaped crystals diffracted X-rays to beyond 1.5 Angstrom at a synchrotron beamline, with space group R3 and unit-cell parameters a = b = 92.26, c = 137.88 Angstrom. A complete data set has been collected to 1.39 Angstrom resolution. The asymmetric unit is estimated and confirmed by self-rotation function calculation to contain two molecules, giving a crystal volume per protein mass (V-M) of 2.68 Angstrom(3) Da(-1) and a solvent content of 54%.