Crystallization and preliminary X-ray analysis of S-ribosylhomocysteinase from Streptococcus mutans.

S-Ribosylhomocysteinase (LuxS) encoded by the luxS gene from Streptococcus mutans plays a crucial role in the quorum-sensing system. LuxS was solubly expressed in Escherichia coli with high yield. The purity of the purified target protein, which was identified by SDS-PAGE and MALDI-TOF MS analysis, was >95%. The protein was crystallized using the hanging-drop vapour-diffusion method with PEG 3350 as the primary precipitant. X-ray diffraction data were collected at Beijing Synchrotron Radiation Facility (BSRF). Diffraction by the crystal extended to 2.4 Å resolution and the crystal belonged to space group C222(1), with unit-cell parameters a = 55.3, b = 148.7, c = 82.8 Å.