Skip to main content
. Author manuscript; available in PMC: 2017 Jun 28.
Published in final edited form as: Biochemistry. 2016 Jun 14;55(25):3586–3593. doi: 10.1021/acs.biochem.6b00180

Figure 4.

Figure 4

Incubation of mouse msrA with H2O2 oxidizes the active site Cys72 to its sulfinic acid. To avoid complications from oxidation or disulfide formation with other cysteine residues, the 3 non-active site cys were mutated to ser [C107S/C218S/C227S].15 The enzyme was incubated for 15 min with or without 1 mM H2O2, then cleaved with chymotrypsin and mapped by HPLC-MS/MS as described.15 The active site Cys72 is contained in the peptide of residues 69–74. The parent peptide’s mass was measured to be 732.2485 Da, and its calculated mass was 732.2480, an error of 0.7 ppm. The expected mass of each b and y ion was calculated by GPMAW and compared to the observed mass, demonstrating that Cys72 was oxidized to the sulfinic acid (represented by a lower case c in the figure). The error in mass measurement for this mass spectrometer in MS-MS mode is ≤ 10 ppm. ND, not detected.