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DNA and Metal Binding of the E. coli Transcription Factor RcnR
Author(s) -
Iwig Jeffrey Scott,
Leitch Sharon,
Maroney Michael,
Chivers Peter
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.782.7
Subject(s) - dna , transcription factor , dna binding protein , transcription (linguistics) , chemistry , nickel , escherichia coli , ligand (biochemistry) , protein family , dna binding site , binding site , metal , biochemistry , biology , genetics , crystallography , promoter , gene , gene expression , receptor , linguistics , philosophy , organic chemistry
Escherichia coli RcnR is a founding member of a new family of bacterial ligand‐responsive transcription factors. RcnR controls the expression of the nickel and cobalt efflux protein RcnA. To better understand the functions of this family, we have investigated the DNA and metal binding properties of RcnR. We find that RcnR binds a pair of inverted repeats in the rcnA promoter. DNA binding is negatively regulated by the direct interaction of RcnR with Ni(II) and Co(II) in vitro and in vivo. X‐ray absorption spectroscopy and mutagenesis experiments reveal a 6‐coordinate metal site with a His 3 (N/O) 2 S ligand set for Ni(II) and Co(II), where the strength of the thiolate interaction allows for discrimination of the two metals. Structural and functional comparisons with the regulatory sites of NikR, another nickel responsive regulator in E. coli, allow for a better understanding of how different nickel levels can be sensed within the same cell. Residues at the N‐terminus of this protein fold are important for recognition of metals that require higher coordination numbers, while the conserved cysteine aids in recognition of metals with the same preferred coordination number. Sequence analysis of other related proteins reveals a four amino acid fingerprint that enables predictions for ligand specificities, leading to an emerging picture of the diversity of this protein family. This work is supported by NSF Grant MCB‐0520877.