1BKA

OXALATE-SUBSTITUTED DIFERRIC LACTOFERRIN

Summary for 1BKA

• Entry DOI: 10.2210/pdb1bka/pdb
• Descriptor: LACTOFERRIN, FE (III) ION, OXALATE ION, ... (4 entities in total)
• Functional Keywords: anion binding, iron binding protein
• Biological source: Homo sapiens (human)
• Cellular location: Secreted: P02788
• Total number of polymer chains: 1
• Total formula weight: 76550.99

Authors

Baker, H.M.,Smith, C.A.,Baker, E.N. (deposition date: 1996-04-15, release date: 1996-11-08, Last modification date: 2024-10-23)

Primary citation

Baker, H.M.,Anderson, B.F.,Brodie, A.M.,Shongwe, M.S.,Smith, C.A.,Baker, E.N.
Anion binding by transferrins: importance of second-shell effects revealed by the crystal structure of oxalate-substituted diferric lactoferrin.
Biochemistry, 35:9007-9013, 1996

PubMed 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 A resolution. The final model has a crystallographic R-factor of 0.196 for all data in the range 8.0-2.4 A. 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" amino 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.

PubMed: 8703903
DOI: 10.1021/bi960288y

Experimental method

X-RAY DIFFRACTION (2.4 Å)