FIG. 2.

NikR is a tetrameric protein. (A) SDS-PAGE of the nickel affinity purified protein preparation of the NikR protein before and after removal of the histidine tag. Lane 1, the purified protein with the histidine tag (His-NikR); lane 2, His-NikR after thrombin digestion and removal of the tag (rNikR); lane M, protein size standards, with molecular masses shown to the left. The arrows indicate the migration of the proteins. The protein was estimated to be 99% pure. (B) Elution profile of the purified rNikR protein from a Superdex 200 HR 10/30 column gel filtration column. The molecular masses corresponding to the peaks of maximal absorbance were calculated after calibration of the peaks with molecular mass standards (67, 43, 25, and 13.7 kDa with elution volumes of 13.52, 14.53, 16.31, and 17 ml, respectively).