title: Iron(III) located in the dinuclear metallo-β-lactamase IMP-1 by pseudocontact shifts.
abstract: Heterodinuclear metalloenzymes are an important class of metalloproteins, but determining the location of the different metal ions can be difficult. Herein we present a new NMR spectroscopy method that uses pseudocontact shifts (PCS) to achieve this without assumptions about the coordinating ligands. The approach is illustrated with the dinuclear [FeZn] complex of IMP-1, which is a prototypical metallo-β-lactamase (MβL) that confers resistance to β-lactam antibiotics. Results from single-crystal X-ray diffraction were compromised by degradation during crystallization. With [GaZn]-IMP-1 as diamagnetic reference, the PCSs unambiguously identified the iron binding site in fresh samples of [FeZn]-IMP-1, even though the two metal centers are less than 3.8 Å apart and the iron is high-spin Fe(3+), which produces only small PCSs. [FeZn]-MβLs may be important drug targets, as [FeZn]-IMP-1 is enzymatically active and readily produced in the presence of small amounts of Fe(3+).
authors.affiliation: Research School of Chemistry, Australian National University, Canberra, ACT 0200 (Australia).
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Carruthers
authors.forename: Paul D
authors.initials: PD
authors.lastname: Carr
authors.forename: Choy-Theng
authors.initials: CT
authors.lastname: Loh
authors.forename: Colin J
authors.initials: CJ
authors.lastname: Jackson
authors.forename: Gottfried
authors.initials: G
authors.lastname: Otting
mesh_terms: D018360:Crystallography, X-Ray; D005290:Ferric Compounds / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D009942:Organometallic Compounds / Q000737:chemistry* / Q000378:metabolism; D001618:beta-Lactamases / Q000737:chemistry* / Q000378:metabolism
chemical_list: D005290:Ferric Compounds; D009942:Organometallic Compounds; C409201:beta-lactamase IMP-1; D001618:beta-Lactamases
keywords: IMP-1; NMR spectroscopy; dinuclear metalloenzymes; metallo-β-lactamase; pseudocontact shifts