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Int J Biol Macromol. 2019 Jul 26;138:1056-1063. doi: 10.1016/j.ijbiomac.2019.07.174. [Epub ahead of print]

A physicochemical investigation on the metal binding properties of TtSmtB, a thermophilic member of the ArsR/SmtB transcription factor family.

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Department of Biology, University of Naples Federico II, Napoli, Italy.
Institute of Biostructure and Bioimaging, CNR, Napoli, Italy.
Department of Chemical Sciences, University of Naples Federico II, Napoli, Italy.
Department of Biology, University of Naples Federico II, Napoli, Italy. Electronic address:


The transcription factors of the ArsR/SmtB family are widespread within the bacterial and archaeal kingdoms. They are transcriptional repressors able to sense a variety of metals and undergo allosteric conformational changes upon metal binding, resulting in derepression of genes involved in detoxification. So far, the molecular determinants of specificity, selectivity, and metal binding mechanism have been scarcely investigated in thermophilic microorganisms. TtSmtB, the only ArsR/SmtB member present in the genome of Thermus thermophilus HB27, was chosen as a model to shed light into such molecular mechanisms at high temperature. In the present study, using a multidisciplinary approach, a structural and functional characterization of the protein was performed focusing on its metal interaction and chemical-physical stability. Our data demonstrate that TtSmtB has two distinct metal binding sites per monomer and interacts with di-tri-penta-valent ions with different affinity. Detailed knowledge at molecular level of protein-metal interaction is remarkable to design metal binding domains as scaffolds in metal-based therapies as well as in metal biorecovery or biosensing in the environment.


ArsR SmtB family; Metal-binding site; Thermostability; Thermus thermophilus; Transcriptional repressor

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