Biochemistry

Cooperating to control cadmium

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Science  18 Oct 2019:
Vol. 366, Issue 6463, pp. 321-322
DOI: 10.1126/science.366.6463.321-g

Cadmium is toxic to living organisms because it displaces essential metal ions in macromolecules. Detoxification systems rely on sulfur-rich sites to coordinate the cadmium, but these sites also bind other heavy metals. Liu et al. show how the bacterium Pseudomonas putida eliminates cadmium. The protein CadR selectively responds to cadmium to bind to DNA and upregulate transcription of itself and other cadmium detoxification proteins. The selectivity comes from cooperation between two types of binding sites. Cadmium first binds to a cysteine-rich site, and this stabilizes the second histidine-rich site in a conformation that supports cadmium binding. Binding at both sites facilitates DNA binding to activate transcription.

Proc. Natl. Acad. Sci. U.S.A. 116, 20398 (2019).

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