Figure 2. Complete Repair of CaM_ox by MsrBA.

(Top) SDS-PAGE (14% Tris-glycine) gel showing time-dependent mobility changes of CaM_ox in the presence of either MsrA or MsrBA. (Bottom) Intact protein ESI-MS spectra of unoxidized CaM (A) and oxidized CaM prior to (B) and following incubation for 12 hours with MsrA (C), MsrB (D), an equimolar mixture of MsrA + MsrB (E), and MsrBA (F). Experimental conditions involved CaM (10 μM) incubated with indicated Msr isoforms (1.0 μM) of either MsrBA, MsrA, or MsrB in 10 mM MOPS (pH 7.5), 50 mM KCl, and 15 mM DTT at 25°C. No MetSO reduction is observed in the absence of added DTT, which acts to reduce the active site of Msr enzymes to permit reduction of MetSO.