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Deuterium exchange mass spectrometry reveals structural dynamics of glucan phosphatases
Author(s) -
Sherwood Amanda,
Gentry Matthew
Publication year - 2010
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.24.1_supplement.863.5
Subject(s) - phosphatase , dual specificity phosphatase , glucan , chemistry , biochemistry , hydrogen–deuterium exchange , biophysics , microbiology and biotechnology , mass spectrometry , enzyme , biology , chromatography
Laforin and Starch Excess 4 (Sex4) are unique phosphatases from humans and plants, respectively, that dephosphorylate phosphoglucans, making them glucan phosphatases. Each protein contains a carbohydrate binding module (CBM) and a dual specificity phosphatase domain (DSP). Mutations in the laforin gene lead to a neurodegenerative disease called Lafora disease (LD). A hallmark of the disease is the presence of hyperphosphorylated, sparsely branched, and thus insoluble glucan accumulations in the cytoplasm. The loss of SEX4 in plants yields a similar accumulation of insoluble glucans. The mechanism by which laforin and SEX4 are believed to dephosphorylate phosphoglucans is unknown, and there is no crystal structure of these phosphatases. We utilized hydrogen‐deuterium exchange mass spectrometry (DXMS) and structural modeling to probe the conformational and structural dynamics of the glucan phosphatase SEX4. Our results suggest that the protein undergoes minimal structural rearrangement upon glucan binding. As expected, the CBM undergoes protection from deuteration upon substrate binding, and surprisingly regions of the DSP also undergo protection. The three regions of the DSP that undergo protection likely participate in substrate presentation to the active site. Collectively, these data provide the first structural analyses and mode of action for this unique class of phosphatases. NIH 5R00NS061803 and 5P20RR020171.