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Characterization of the pH‐dependent dissociation of a multimeric metalloprotein Streptomyces rubiginosus xylose isomerase by ESI FT‐ICR mass spectrometry
Author(s) -
Jänis Janne,
Pasanen Salla,
Rouvinen Juha,
Vainiotalo Pirjo
Publication year - 2008
Publication title -
journal of mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 1076-5174
DOI - 10.1002/jms.1413
Subject(s) - chemistry , tetramer , fourier transform ion cyclotron resonance , mass spectrometry , electrospray ionization , dissociation (chemistry) , xylose isomerase , stereochemistry , isomerase , enzyme , chromatography , biochemistry , organic chemistry
We report an analysis of the pH‐dependent dissociation of a multimeric metalloprotein, xylose isomerase from Streptomyces rubiginosus (XI), by electrospray ionization (ESI) Fourier transform ion cyclotron resonance (FT‐ICR) mass spectrometry. Xylose isomerases are industrially significant enzymes that catalyze interconversion of aldose and ketose sugars. XI is biologically active as a ∼173‐kDa tetrameric complex, comprised of four identical ∼43‐kDa subunits and eight metal cations, unequivocally identified as the Mg 2+ cations in this work. ESI FT‐ICR mass spectra of XI measured in the pH range of 3.0–6.9 indicated that the dissociation of the intact holo ‐tetramer is initiated by the loss of all eight Mg 2+ cations at pH ≤5.0, followed by step‐by‐step dissociation of the remaining apo ‐tetramer to trimers, dimers and monomers. In addition, a ∼346‐kDa protein octamer was detected at pH 6.9. Copyright © 2008 John Wiley & Sons, Ltd.