Charge compensated binding of divalent metals to bacterioferritin: H+ release associated with cobalt(II) and zinc(II) binding at dinuclear metal sites

FEBS Letters

C. Andrews, Simon³  Grant Mauk, A.²  E. Le Brun, Nick¹  M. Keech, Angus¹  J. Thomson, Andrew¹  R. Moore, Geoffrey¹  R. Mauk, Marcia² 

[1] Centre for Metalloprotein Spectroscopy and Biology, School of Chemical Sciences, University of East Anglia, Norwich NR4 7TJ, UK;Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada;The Krebs Institute, Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield SIO 2UH, UK

关键词: Bacterioferritin;    Dinuclear center;    Cobalt(II);    Zinc(ll);    Potentiometry;    Charge neutrality;   

DOI  :  10.1016/S0014-5793(96)01172-6

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Divalent metal ion binding to the bacterial iron-storage protein, bacterioferritin (BFR), which contains a dinuclear metal binding site within each of its 24 subunits, was investigated by potentiometric and spectrophotometric methods. Cobalt(II) and zinc(II) were found to bind at both high- and low-affinity sites. Cobalt(II) binding at the high-affinity site was observed at a level of two per subunit with the release of ∼ 1.6 protons per metal ion, thus confirming the dinuclear metal centre as the high-affinity site. Zinc(II) binding at the dinuclear centre (high-affinity site) resulted in the release of ∼ 2 protons per metal ion, but exhibited a binding stoichiometry which indicated that not all dinuclear centres were capable of binding two zinc(II) ions. Competition data showed that binding affinities for the dinuclear centre were in the order zinc(II) > cobalt(II), and also confirmed the unexpected stoichiometry of zinc(II) binding. This work emphasises the importance ∼ of charge neutrality at the dinuclear centre.

【 授权许可】

Unknown