Observation of the iron-sulfur cluster in Escherichia coli biotin synthaseby nanoflow electrospray mass spectrometry

Citation
H. Hernandez et al., Observation of the iron-sulfur cluster in Escherichia coli biotin synthaseby nanoflow electrospray mass spectrometry, ANALYT CHEM, 73(17), 2001, pp. 4154-4161
Citations number
42
Categorie Soggetti
Chemistry & Analysis","Spectroscopy /Instrumentation/Analytical Sciences
Journal title
ANALYTICAL CHEMISTRY
ISSN journal
00032700 → ACNP
Volume
73
Issue
17
Year of publication
2001
Pages
4154 - 4161
Database
ISI
SICI code
0003-2700(20010901)73:17<4154:OOTICI>2.0.ZU;2-G
Abstract
Biotin synthase from Escherichia coli was analyzed by nanoflow electrospray ionization mass spectrometry. From solution conditions in which the protei n is in its native state, a distribution of monomeric, dimeric, and tetrame ric species was observed. The distribution of these species was sensitive t o changes in ionic strength: in the positive ion spectrum, biotin synthase at low ionic strength (pH 7.0-8.5) yielded less than 10% dimer. The masses of the monomeric species were consistent with the presence of a [2Fe-2S] cl uster with a mass difference of 175.3 Da from the apomonomer with one disul fide bond. Despite the molecular mass of the noncovalent dimer (77 kDa), it was possible to observe a dimeric species containing one iron-sulfur clust er in both positive and negative ion spectra. Additionally, observation of a series of charge states assigned to the apodimer indicated that binding o f the iron-sulfur cluster was not required to maintain the dimer. Binding o f Cu2+ to biotin synthase was also observed; in the presence of excess chel ating agent, free metals were removed and the iron-sulfur cluster remained intact. Evidence for the coordination of the iron-sulfur cluster in biotin synthase was obtained in a tandem mass spectrometry experiment. A single ch arge state containing the cluster at m/z 2416.9 was isolated, and collision -induced dissociation resulted in sequential loss of sulfur and retention o f Fe3+.