Zinc finger (ZF) proteins use zinc ion as a structural co-factor and are often involved in nucleic acid recognition and binding. Although zinc is typically thought to be the physiologically relevant transition-metal ion for ZF protein function, there is evidence that other metal ions, including iron, may replace zinc under certain conditions. Studies focused on the roles of metal coordination and DNA binding for two specific ZF proteins: ST18 (suppression of tumorogenecity 18) and ZIF268 (zinc interacting factor 268) will be presented. ST18 is a non-classical ZF that belongs to the NZF/MyT family of ZFs. It contains six ZF domains, each of which has a Cys2His2Cys motif. The biological function of ST18 is not well understood; however, there is some recent evidence that ST18 regulates inflammation and apoptosis by regulating gene expression of tumor necrosis factor-alpha (TNF-α). We have been studying constructs of ST18 that contain the Cys2His2Cys domains, and have obtained evidence for zinc binding. These studies along with DNA binding studies with the TNF-α promoter will be presented. ZIF268 is a classical zinc finger protein that utilizes a Cys2His2 ligand set to bind zinc and fold into a characteristic β2α structure. The zinc and DNA binding properties of ZIF268 are well understood and it is possible to modify the protein sequence to tune DNA recognition. As part of an effort to understand the role of metal ion identity in function, we performed optical titrations of ZIF268 with ferrous and ferric iron followed by DNA binding studies (monitored by fluorescence anisotropy). We discovered that both ferric and ferrous iron binds to ZIF268, and both forms can bind to target DNA with comparable affinity to Zn-ZIF268; however, the iron bound forms are more susceptible to oxidation than zinc. References: Lee, S. J. and Michel, S. L. J. Accounts of Chemical Research, 2014, 47, 2643-2650 Lee, S. J., Michalek, J., Besold, A., Rokita, S.E., Michel, S.L.J. Inorganic Chemistry, 2011, 50, 5442-5450

Metal coordination and DNA interaction studies of classical and non-classical zinc fingers

251st National Meeting (2016)

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