Anion binding by transferrins

Importance of second-shell effects revealed by the crystal structure of oxalate-substituted diferric lactoferrin

Heather M. Baker, Bryan F. Anderson, Andrew M. Brodie, Musa S. Shongwe, Clyde A. Smith, Edward N. Baker

Research output: Contribution to journalArticle

39 Citations (Scopus)

Abstract

Proteins of the transferrin family bind, with high affinity, two Fe3+ ions and two CO3 2- ions but can also bind other metal ions and other anions. In order to find out how the protein structure and its two binding sites adapt to the binding of larger anions, we have determined the crystal structure of oxalate-substituted diferric lactoferrin at 2.4 Å resolution. The final model has a crystallographic R-factor of 0.196 for all data in the range 8.0-2.4 Å. Substitution of oxalate for carbonate does not produce any significant change in the polypeptide folding or domain closure. Both binding sites are perturbed, however, and the effects are different in each. In the C-lobe site the oxalate ion is bound to iron in symmetric 1,2-bidentate fashion whereas in the N-lobe the anion coordination is markedly asymmetric. The difference arises because in each site substitution of the larger anion causes displacement of the arginine that forms one wall of the anion binding site: the movement is different in each case, however, because of different interactions with 'second shell' amine acid residues in the binding cleft. These observations provide an explanation for the site inequivalences that accompany the substitution of non-native anions and cations.

Original languageEnglish
Pages (from-to)9007-9013
Number of pages7
JournalBiochemistry
Volume35
Issue number28
DOIs
Publication statusPublished - 1996

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Transferrins
Shells (structures)
Lactoferrin
Oxalates
Anions
Crystal structure
Ions
Substitution reactions
Binding Sites
R388
Carbonates
Transferrin
Amines
Metal ions
Arginine
Cations
Proteins
Iron
Metals
Peptides

ASJC Scopus subject areas

  • Biochemistry

Cite this

Anion binding by transferrins : Importance of second-shell effects revealed by the crystal structure of oxalate-substituted diferric lactoferrin. / Baker, Heather M.; Anderson, Bryan F.; Brodie, Andrew M.; Shongwe, Musa S.; Smith, Clyde A.; Baker, Edward N.

In: Biochemistry, Vol. 35, No. 28, 1996, p. 9007-9013.

Research output: Contribution to journalArticle

Baker, Heather M. ; Anderson, Bryan F. ; Brodie, Andrew M. ; Shongwe, Musa S. ; Smith, Clyde A. ; Baker, Edward N. / Anion binding by transferrins : Importance of second-shell effects revealed by the crystal structure of oxalate-substituted diferric lactoferrin. In: Biochemistry. 1996 ; Vol. 35, No. 28. pp. 9007-9013.
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