Expression, purification and crystallization of Enterococcus faecium streptogramin A acetyltransferase

The streptogramin A acetyltransferase from Enterococcus faecium (SWISS-PROT P50870) has been overexpressed in Escherichia coli, purified and crystallized. Crystallization conditions were screened using the hanging-drop vapor-diffusion method and resulted in two distinct crystal forms. Form I crystals diffract to 2.5 Å and belong to space group P2₁2₁2₁, with unit-cell parameters a = 68.6, b = 102.6, c = 107.5 Å. Form II crystals diffract to 2.7 Å and belong to space group F222, with unit-cell parameters a = 185.8, b = 185.8, c = 186.5 Å. Rotation-function and packing analyses for both crystal forms indicate that the asymmetric unit may contain one and two copies of the trimeric enzyme for crystal forms I and II, respectively.