Purification and factor Xa cleavage of MBP-MrsD fusion protein. (A) Purification and factor Xa cleavage of MBP-MrsD was followed by SDS-PAGE. Lanes: M, molecular mass marker (sizes are in kilodaltons in the left margin); 1 and 2, whole-cell lysate of E. coli TB1(pIH902 mrsD) before and after induction with IPTG; 3, cleared cell lysate; 4, MBP-MrsD purified by amylose affinity chromatography; 5 to 8, cleavage of MBP-MrsD with factor Xa after 1, 2, 3, and 17.5 h of incubation at room temperature, respectively. (B) Absorption spectra of purified MBP-MrsD (black line) and purified MBP-EpiD (gray line).