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Figure 5
Mass spectrometry was performed on cleaved (non-His-tagged) RtGH124 to study the His264 modification. (a) ESI-MS, general and enlarged (inset) spectra. The two main peaks indicate a mixture of non-oxidized (calculated, 25 304 Da; observed, 25 298 Da) and oxidized (calculated, 25 320 Da; observed, 25 315 Da) forms. The difference in the observed and calculated sizes is within the error range for this technique. (b) The peptide resulting from the proteolysis of cleaved RtGH124 (GISVHMGIR) was analysed by LC-MS/MS. A mixture of unoxidized (in green) and oxidized (in pink) forms was also observed as a shift of 16 Da in the peaks of peptides containing His264. (c) The form of `2-oxohistidine' observed here is that which gives the +16 mass shift [as described in Schöneich (2000BB22) and observed in the B. subtilis PerR structure (Traoré et al., 2009BB28)] and not the chemically distinct +14 species.

ISSN: 2053-230X
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