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Analysis of the metal‐binding selectivity of the metallochaperone CopZ from Enterococcus hirae by electrospray ionization mass spectrometry
Author(s) -
Urvoas Agathe,
Amekraz Badia,
Moulin Christophe,
Le Clainche Loïc,
Stöcklin Reto,
Moutiez Mireille
Publication year - 2003
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.1130
Subject(s) - enterococcus hirae , chemistry , electrospray ionization , dissociation constant , metal , copper , mass spectrometry , metal ions in aqueous solution , analytical chemistry (journal) , stereochemistry , crystallography , inorganic chemistry , chromatography , organic chemistry , biochemistry , receptor , enterococcus , antibiotics
Metallochaperones are soluble proteins involved in metal transport and regulation in vivo . Copper metallochaperones belong to a structural family of metal binding domains displaying a ferredoxin‐like fold ( βαββαβ ) and a consensus metal‐binding motif MXCXXC. The metal‐binding selectivities for this class of proteins are poorly documented so far. The present study focuses on the measurement of the selectivity of the copper metallochaperone CopZ from Enterococcus hirae for different metal ions using an experimental approach based on electrospray ionization mass spectrometry (ESI‐MS). All the metal cations tested, i.e. Cu(I), Cu(II), Hg(II), Cd(II) and Co(II), form specific metal complexes with CopZ. The study of a chemically modified CopZ as well as variants of CopZ in the active site demonstrated that the complexes observed by ESI‐MS, i.e. in the gas phase, corresponded to the complexes previously observed by other analytical methods in solution. Competition experiments allowed the classification of the metal ions by increasing affinities for CopZ as follows: Co ≪ Cd < Hg < Cu. A dissociation constant in the range of 20 μM was determined for cobalt. The affinity of CopZ for the other metals tested was found to be higher, with dissociation constants smaller than micromolar. Copyright © 2003 John Wiley & Sons, Ltd.