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Hoffmann, R. A wiki for the life sciences where authorship matters. Nature Genetics (2008)
 
 
 
 
 

Characterization of the catalase-peroxidase KatG from Burkholderia pseudomallei by mass spectrometry.

The electron density maps of the catalase-peroxidase from Burkholderia pseudomallei (BpKatG) presented two unusual covalent modifications. A covalent structure linked the active site Trp111 with Tyr238 and Tyr238 with Met264, and the heme was modified, likely by a perhydroxy group added to the vinyl group on ring I. Mass spectrometry analysis of tryptic digests of BpKatG revealed a cluster of ions at m/z 6585, consistent with the fusion of three peptides through Trp111, Tyr238, and Met264, and a cluster at m/z approximately 4525, consistent with the fusion of two peptides linked through Trp111 and Tyr238. MS/MS analysis of the major ions at m/z 4524 and 4540 confirmed the expected sequence and suggested that the multiple ions in the cluster were the result of multiple oxidation events and transfer of CH3-S to the tyrosine. Neither cluster of ions at m/z 4525 or 6585 was present in the spectrum of a tryptic digest of the W111F variant of BpKatG. The spectrum of the tryptic digest of native BpKatG also contained a major ion for a peptide in which Met264 had been converted to homoserine, consistent with the covalent bond between Tyr238 and Met264 being susceptible to hydrolysis, including the loss of the CH3-S from the methionine. Analysis of the tryptic digests of hydroperoxidase I (KatG) from Escherichia coli provided direct evidence for the covalent linkage between Trp105 and Tyr226 and indirect evidence for a covalent linkage between Tyr226 and Met252. Tryptic peptide analysis and N-terminal sequencing revealed that the N-terminal residue of BpKatG is Ser22.[1]

References

  1. Characterization of the catalase-peroxidase KatG from Burkholderia pseudomallei by mass spectrometry. Donald, L.J., Krokhin, O.V., Duckworth, H.W., Wiseman, B., Deemagarn, T., Singh, R., Switala, J., Carpena, X., Fita, I., Loewen, P.C. J. Biol. Chem. (2003) [Pubmed]
 
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