Anion binding by human lactoferrin: Results from crystallographic and physicochemical studies

Musa S. Shongwe, Clyde A. Smith, Eric W. Ainscough, Heather M. Baker, Andrew M. Brodie, Edward N. Baker

Research output: Contribution to journalArticle

59 Citations (Scopus)

Abstract

The anion-binding properties of lactoferrin (Lf), with Fe3+ or Cu2+ as the associated metal ion, have been investigated by physicochemical and crystallographic techniques. These highlight differences between the two sites and in the anion-binding behavior when different metals are bound. Carbonate, oxalate, and hybrid carbonane-oxalate complexes have been prepared and their characteristic electronic and EPR spectra recorded. Oxalate can displace carbonate from either one or both anion sites of Cu2(CO3)2Lf, depending on the oxalate concentration, but no such displacement occurs for Fe2(CO3)2Lf. Addition of oxalate and the appropriate metal ion to apoLf under carbonate-free conditions gives dioxalate complexes with both Fe3+ and Cu2+, except when traces of EDTA remain associated with the protein, when hybrid complexes M2(CO3)(C2O4)Lf can result. The anion sites in the crystal structures of Fe2(CO3)2Lf, Cu2-(CO3)2Lf, and Cu2(CO3)(C2O4)Lf, refined at 2.2, 2.1, and 2.2 Å, respectively, have been compared. In every case, the anion is hydrogen bonded to the N-terminus of helix 5, an associated arginine side chain, and a nearby threonine side chain. The carbonate ion binds in bidentate fashion to the metal, except in the N-lobe site of dicupric lactoferrin, where it is monodentate; the difference arises from slight movement of the metal ion. The hybrid complex shows that the oxalate ion binds preferentially in the C-lobe site, in 1,2-bidentate mode, but with the displacement of several nearby side chains. These observations lead to a generalized model for synergistic anion binding by transferrins.

Original languageEnglish
Pages (from-to)4451-4458
Number of pages8
JournalBiochemistry
Volume31
Issue number18
Publication statusPublished - 1992

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Lactoferrin
Oxalates
Anions
Carbonates
Metals
Ions
Metal ions
Transferrins
Threonine
Edetic Acid
Paramagnetic resonance
Arginine
Hydrogen
Crystal structure
Proteins

ASJC Scopus subject areas

  • Biochemistry

Cite this

Shongwe, M. S., Smith, C. A., Ainscough, E. W., Baker, H. M., Brodie, A. M., & Baker, E. N. (1992). Anion binding by human lactoferrin: Results from crystallographic and physicochemical studies. Biochemistry, 31(18), 4451-4458.

Anion binding by human lactoferrin : Results from crystallographic and physicochemical studies. / Shongwe, Musa S.; Smith, Clyde A.; Ainscough, Eric W.; Baker, Heather M.; Brodie, Andrew M.; Baker, Edward N.

In: Biochemistry, Vol. 31, No. 18, 1992, p. 4451-4458.

Research output: Contribution to journalArticle

Shongwe, MS, Smith, CA, Ainscough, EW, Baker, HM, Brodie, AM & Baker, EN 1992, 'Anion binding by human lactoferrin: Results from crystallographic and physicochemical studies', Biochemistry, vol. 31, no. 18, pp. 4451-4458.
Shongwe MS, Smith CA, Ainscough EW, Baker HM, Brodie AM, Baker EN. Anion binding by human lactoferrin: Results from crystallographic and physicochemical studies. Biochemistry. 1992;31(18):4451-4458.
Shongwe, Musa S. ; Smith, Clyde A. ; Ainscough, Eric W. ; Baker, Heather M. ; Brodie, Andrew M. ; Baker, Edward N. / Anion binding by human lactoferrin : Results from crystallographic and physicochemical studies. In: Biochemistry. 1992 ; Vol. 31, No. 18. pp. 4451-4458.
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