title: Ferric ion (hydr)oxo clusters in the "Venus flytrap" cleft of FbpA: Mössbauer, calorimetric and mass spectrometric studies.
abstract: Isothermal calorimetric studies of the binding of iron(III) citrate to ferric ion binding protein from Neisseria gonorrhoeae suggested the complexation of a tetranuclear iron(III) cluster as a single step binding event (apparent binding constant K(app) (ITC) = 6.0(5) × 10(5) M(-1)). High-resolution Fourier transform ion cyclotron resonance mass spectrometric data supported the binding of a tetranuclear oxo(hydroxo) iron(III) cluster of formula [Fe(4)O(2)(OH)(4)(H(2)O)(cit)](+) in the interdomain binding cleft of FbpA. The mutant H9Y-nFbpA showed a twofold increase in the apparent binding constant [K(app) (ITC) = 1.1(7) × 10(6) M(-1)] for the tetranuclear iron(III) cluster compared to the wild-type protein. Mössbauer spectra of Escherichia coli cells overexpressing FbpA and cultured in the presence of added (57)Fe citrate were indicative of the presence of dinuclear and polynuclear clusters. FbpA therefore appears to have a strong affinity for iron clusters in iron-rich environments, a property which might endow the protein with new biological functions.
authors.affiliation: Department of Chemical Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur Campus, Nadia 741252, India.
authors.forename: Arindam
authors.initials: A
authors.lastname: Mukherjee
authors.forename: Paul R
authors.initials: PR
authors.lastname: Bilton
authors.forename: Logan
authors.initials: L
authors.lastname: Mackay
authors.forename: Adam
authors.initials: A
authors.lastname: Janoschka
authors.forename: Haizhong
authors.initials: H
authors.lastname: Zhu
authors.forename: Dean
authors.initials: D
authors.lastname: Rea
authors.forename: Pat R R
authors.initials: PR
authors.lastname: Langridge-Smith
authors.forename: Dominic J
authors.initials: DJ
authors.lastname: Campopiano
authors.forename: Thomas
authors.initials: T
authors.lastname: Teschner
authors.forename: Alfred X
authors.initials: AX
authors.lastname: Trautwein
authors.forename: Volker
authors.initials: V
authors.lastname: Schünemann
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Sadler
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics; D001665:Binding Sites; D002151:Calorimetry; D003001:Cloning, Molecular; D005290:Ferric Compounds / Q000737:chemistry*; D033862:Iron-Binding Proteins / Q000737:chemistry* / Q000235:genetics; D013058:Mass Spectrometry; D008958:Models, Molecular; D015394:Molecular Structure; D009344:Neisseria gonorrhoeae; D015204:Spectroscopy, Mossbauer
chemical_list: D001426:Bacterial Proteins; D005290:Ferric Compounds; D033862:Iron-Binding Proteins