Ni(II) And Co(II) Sensing By Escherichia Coli RcnR

Journal Article · Mon May 18 04:00:00 EDT 2009 · J. Am. Chem. Soc 130:7592,2008

OSTI ID:953126

Iwig, J S; Leitch, S; Herbst, R W; Maroney, M J; Chivers, P T

Escherichia coli RcnR and Mycobacterium tuberculosis CsoR are the founding members of a recently identified, large family of bacterial metal-responsive DNA-binding proteins. RcnR controls the expression of the metal efflux protein RcnA only in response to Ni(II) and Co(II) ions. Here, the interaction of Ni(II) and Co(II) with wild-type and mutant RcnR proteins is examined to understand how these metals function as allosteric effectors. Both metals bind to RcnR with nanomolar affinity and stabilize the protein to denaturation. X-ray absorption and electron paramagnetic resonance spectroscopies reveal six-coordinate high-spin sites for each metal that contains a thiolate ligand. Experimental data support a tripartite N-terminal coordination motif (NH{sub 2}-Xaa-NH-His) that is common for both metals. However, the Ni(II)- and Co(II)-RcnR complexes are shown to differ in the remaining coordination environment. Each metal coordinates a conserved Cys ligand but with distinct M-S distances. Co(II)-thiolate coordination has not been observed previously in Ni(II)-/Co(II)-responsive metalloregulators. The ability of RcnR to recruit ligands from the N-terminal region of the protein distinguishes it from CsoR, which uses a lower coordination geometry to bind Cu(I). These studies facilitate comparisons between Ni(II)-RcnR and NikR, the other Ni(II)-responsive transcriptional regulator in E. coli, to provide a better understanding how different nickel levels are sensed in E. coli. The characterization of the Ni(II)- and Co(II)-binding sites in RcnR, in combination with bioinformatics analysis of all RcnR/CsoR family members, identified a four amino acid fingerprint that likely defines ligand-binding specificity, leading to an emerging picture of the similarities and differences between different classes of RcnR/CsoR proteins.

• Research Organization: Stanford Linear Accelerator Center (SLAC)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC02-76SF00515
• OSTI ID: 953126
• Report Number(s): SLAC-REPRINT-2009-158
• Journal Information: J. Am. Chem. Soc 130:7592,2008, Journal Name: J. Am. Chem. Soc 130:7592,2008 Journal Issue: 24 Vol. 130
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
ABSORPTION
AFFINITY
AMINO ACIDS
ELECTRON SPIN RESONANCE
ESCHERICHIA COLI
GEOMETRY
MUTANTS
MYCOBACTERIUM TUBERCULOSIS
NICKEL
Other
OTHER
COMP
PROTEINS
SPECIFICITY