A novel protein–mineral interface

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Abstract
Transferrins transport Fe3+ and other metal ions in mononuclear-binding sites. We present the first evidence that a member of the transferrin superfamily is able to recognize multi-nuclear oxo-metal clusters, small mineral fragments that are the most abundant forms of many metals in the environment. We show that the ferric ion–binding protein from Neisseria gonorrhoeae (nFbp) readily binds clusters of Fe3+, Ti4+, Zr4+ or Hf4+ in solution. The 1.7 Å resolution crystal structure of Hf–nFbp reveals three distinct types of clusters in an open, positively charged cleft between two hinged protein domains. A di-tyrosyl cluster nucleation motif (Tyr195-Tyr196) is situated at the bottom of this cleft and binds either a trinuclear oxo-Hf cluster, which is capped by phosphate, or a pentanuclear cluster, which in turn can be capped with phosphate. This first high-resolution structure of a protein–mineral interface suggests a novel metal-uptake mechanism and provides a model for protein-mediated mineralization/dissimilation, which plays a critical role in geochemical processes. NOTE: In the version of this article initially published online, the institution affiliations were assigned incorrectly because of a mistake that occurred during production. The correct affiliations for all authors are as follows: Dmitriy Alexeev1, Haizhong Zhu2, Maolin Guo2,3, Weiqing Zhong2,4, Dominic J.B. Hunter2, Weiping Yang2,3, Dominic J. Campopiano2 and Peter J. Sadler2. All of the footnotes (corrected) are as follows: 1Institute of Cell and Molecular Biology, Michael Swann Building, University of Edinburgh, Mayfield Road, Edinburgh EH9 3JR, UK; 2School of Chemistry, University of Edinburgh, West Mains Road, Edinburgh EH9 3JJ, UK; 3Current address: Department of Molecular Biology and Biochemistry, University of California, Irvine, California 92697, USA; and 4Current address: School of Pharmacy, Second Military Medicine University, Shanghai 200433, China. We apologize for any inconvenience this may have caused. This mistake has been corrected in the HTML and print version of the article.