A, Western blot showing the production of STM2200 in pBADA2 vector in whole cell lysates using an alkaline phosphatase-conjugated anti-His antibody. Lane M, marker; lane 1, control expression without induction; lane 2, expression after 3 h of induction with 0.02% (w/v) l-arabinose; lane 3, expression after 4 h of induction with 0.02% (w/v) l-arabinose. B, Western blot of small scale production of STM2200 and its four variants, i.e. K163A, K163L, R395M, and E222L. STM2200 and its variants were produced in small scale. Whole cell lysates were prepared, and equal amounts of total protein were subjected to SDS-PAGE and subsequent Western blotting using anti-His antibodies. Lane M, protein marker; lane 1, uninduced STM2200 as a negative control; lane 2, induced STM2200 as a positive control; lane 3, uninduced K163A; lane 4, induced K163A; lane 5, uninduced K163L; lane 6, induced K163L; lane 7, uninduced R395M; lane 8, induced R395M; lane 9, uninduced E222L; lane 10, induced E222L. C, Coomassie-stained 10% SDS-polyacrylamide gel shows purified STM2200. D, analytical gel filtration profile of purified STM2200 using a Superdex 200 column in a SMART system in buffer containing 20 mm MES-NaOH, 150 mm NaCl, 0.025% (w/v) β-DDM, pH 5.92.