title: Structure, properties, and engineering of the major zinc binding site on human albumin.
abstract: Most blood plasma zinc is bound to albumin, but the structure of the binding site has not been determined. Zn K-edge extended x-ray absorption fine structure spectroscopy and modeling studies show that the major Zn(2+) site on albumin is a 5-coordinate site with average Zn-O/N distances of 1.98 A and a weak sixth O/N bond of 2.48 A, consistent with coordination to His(67) and Asn(99) from domain I, His(247) and Asp(249) from domain II (residues conserved in all sequenced mammalian albumins), plus a water ligand. The dynamics of the domain I/II interface, thought to be important to biological function, are affected by Zn(2+) binding, which induces cooperative allosteric effects related to those of the pH-dependent neutral-to-base transition. N99D and N99H mutations enhance Zn(2+) binding but alter protein stability, whereas mutation of His(67) to alanine removes an interdomain H-bond and weakens Zn(2+) binding. Both wild-type and mutant albumins promote the safe management of high micromolar zinc concentrations for cells in cultures.
authors.affiliation: Department of Chemistry, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, United Kingdom. c.blindauer@warwick.ac.uk
authors.forename: Claudia A
authors.initials: CA
authors.lastname: Blindauer
authors.forename: Ian
authors.initials: I
authors.lastname: Harvey
authors.forename: Kerry E
authors.initials: KE
authors.lastname: Bunyan
authors.forename: Alan J
authors.initials: AJ
authors.lastname: Stewart
authors.forename: Darrell
authors.initials: D
authors.lastname: Sleep
authors.forename: David J
authors.initials: DJ
authors.lastname: Harrison
authors.forename: Stephen
authors.initials: S
authors.lastname: Berezenko
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Sadler
mesh_terms: D001665:Binding Sites; D002460:Cell Line; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D009154:Mutation; D011485:Protein Binding; D015202:Protein Engineering; D017433:Protein Structure, Secondary; D012709:Serum Albumin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D013329:Structure-Activity Relationship; D015032:Zinc / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D012709:Serum Albumin; D015032:Zinc