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Top‐down structural analysis of posttranslationally modified proteins by Fourier transform ion cyclotron resonance‐ MS with hydrogen/deuterium exchange and electron capture dissociation
Author(s) -
Pan Jingxi,
Borchers Christoph H.
Publication year - 2013
Publication title -
proteomics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.26
H-Index - 167
eISSN - 1615-9861
pISSN - 1615-9853
DOI - 10.1002/pmic.201200246
Subject(s) - hydrogen–deuterium exchange , electron capture dissociation , chemistry , fourier transform ion cyclotron resonance , calmodulin , crystallography , mass spectrometry , protein structure , amide , biochemistry , enzyme , chromatography
High‐resolution structural characterization of posttranslationally modified proteins represents a challenge for traditional structural biology methods such as crystallography and NMR . In this study, we have used top‐down hydrogen/deuterium exchange MS ( HDX ‐ MS ) with precursor ion selection and electron capture dissociation to determine the impact of oxidative modification on calmodulin ( C a M ) at an average resolution of 2.5 residues, with complete sequence coverage. The amide deuteration status of native C a M determined by this method correlates well with previously reported crystallographic and NMR data. In contrast, methionine oxidation caused almost complete deuteration of all residues in the protein in 10 s. The oxidative‐modification‐induced secondary and tertiary structure loss can be largely recovered upon calcium ligation, which also resulted in a substantial increase of amide protection in three of the four calcium‐binding loops in oxidatively modified C a M ( C a M ox ). However, the structure of α‐helix VI is not restored by cofactor binding. These results are discussed in terms of different target binding and activation capabilities displayed by C a M and C a M ox . The isoform‐specific top‐down HDX structural analysis strategy demonstrated in this study should be readily applicable to other oxidatively modified proteins and other types of PTM s, and may help decipher the structure and function of specific protein isoforms.