Co(II) and Ni(II) binding of the Escherichia coli transcriptional repressor RcnR orders its N terminus, alters helix dynamics, and reduces DNA affinity.

Autor:	Huang HT; Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003., Bobst CE; Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003., Iwig JS; Carmot Therapeutics, Inc., San Francisco, California 94158., Chivers PT; Departments of Biosciences and Chemistry, Durham University, Durham DH1 3LE, United Kingdom., Kaltashov IA; Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003., Maroney MJ; Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003. Electronic address: mmaroney@chem.umass.edu.
Jazyk:	angličtina
Zdroj:	The Journal of biological chemistry [J Biol Chem] 2018 Jan 05; Vol. 293 (1), pp. 324-332. Date of Electronic Publication: 2017 Nov 17.
DOI:	10.1074/jbc.RA117.000398
Abstrakt:	RcnR, a transcriptional regulator in Escherichia coli , derepresses the expression of the export proteins RcnAB upon binding Ni(II) or Co(II). Lack of structural information has precluded elucidation of the allosteric basis for the decreased DNA affinity in RcnR's metal-bound states. Here, using hydrogen-deuterium exchange coupled with MS (HDX-MS), we probed the RcnR structure in the presence of DNA, the cognate metal ions Ni(II) and Co(II), or the noncognate metal ion Zn(II). We found that cognate metal binding altered flexibility from the N terminus through helix 1 and modulated the RcnR-DNA interaction. Apo-RcnR and RcnR-DNA complexes and the Zn(II)-RcnR complex exhibited similar 2 H uptake kinetics, with fast-exchanging segments located in the N terminus, in helix 1 (residues 14-24), and at the C terminus. The largest difference in 2 H incorporation between apo- and Ni(II)- and Co(II)-bound RcnR was observed in helix 1, which contains the N terminus and His-3, and has been associated with cognate metal binding. 2 H uptake in helix 1 was suppressed in the Ni(II)- and Co(II)-bound RcnR complexes, in particular in the peptide corresponding to residues 14-24, containing Arg-14 and Lys-17. Substitution of these two residues drastically affected DNA-binding affinity, resulting in rcnA expression in the absence of metal. Our results suggest that cognate metal binding to RcnR orders its N terminus, decreases helix 1 flexibility, and induces conformational changes that restrict DNA interactions with the positively charged residues Arg-14 and Lys-17. These metal-induced alterations decrease RcnR-DNA binding affinity, leading to rcnAB expression. (© 2018 by The American Society for Biochemistry and Molecular Biology, Inc.)
Databáze:	MEDLINE
Externí odkaz: