Molecular Playground/CsoR and RcnR: Difference between revisions

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Heidi Hu, Michal Harel, Carolyn Carr, Hsin-Ting Huang, Alexander Berchansky

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 In [http://en.wikipedia.org/wiki/Escherichia_coli ''Escherichia coli''] apo-RcnR blocks the transcription of nickel and cobalt efflux proteins RcnA and RcnB by binding to its promoter region.  Although no crystal structure of RcnR is available on the PDB, the Cu(I)-bound CsoR crystal structure from [http://en.wikipedia.org/wiki/Mycobacterium_tuberculosis ''Mycobacterium tuberculosis''] is available and RcnR is predicted to share a similar fold to CsoR.  Upon Ni(II)- or Co(II)-binding, RcnR is released from DNA allowing the transcription of RcnA and RcnB, facilitating the efflux of Ni(II) and Co(II).<ref>PMID:20442957</ref>   CsoR has been characterized in [http://en.wikipedia.org/wiki/Bacillus_subtilis ''Bacillus subtilis'']<ref>PMID:18048925</ref> and [http://en.wikipedia.org/wiki/Mycobacterium_tuberculosis ''M. tuberculosis'']<ref>PMID:17143269</ref> to release from the promoter regions of copper-efflux operons upon binding of Cu(I).  The analogous functions of CsoR and RcnR in addition to local sequence similarity (25% identical, 56% similar) suggests a conserved mode of function in this family of metal-responsive DNA-binding proteins.<ref>PMID:18505253</ref>
-== CsoR Structure ==
+== Structure of CsoR and RcnR ==
 <scene name='Heidi_Hu/Sandbox_1/Tetrameric_csor/1'>Tetrameric CsoR</scene> binds one Cu(I) per monomer.  The protein forms a dimer of dimers with a
-<scene name='Heidi_Hu/Sandbox_1/Tetrameric_csor/5'>pore</scene> in the tetrameric interface. Each <scene name='Heidi_Hu/Sandbox_1/Tetrameric_csor/10'>Cu(I) coordinated by two different monomers</scene> of a dimer unit.  Where one monomer is bound to Cu(I) by His61 and Cys65, the other monomer is bound to the metal by Cys35.<ref>PMID:17143269</ref>  [http://en.wikipedia.org/wiki/Escherichia_coli ''E. coli''] RcnR is also tetrameric and has the same protein-to-metal stochiometry.
+<scene name='Heidi_Hu/Sandbox_1/Tetrameric_csor/5'>pore</scene> in the tetrameric interface. Each <scene name='Heidi_Hu/Sandbox_1/Tetrameric_csor/10'>Cu(I) coordinated by two different monomers</scene> of a dimer unit.  Where one monomer is bound to Cu(I) by His61 and Cys65, the other monomer is bound to the metal by Cys35.<ref>PMID:17143269</ref>  [http://en.wikipedia.org/wiki/Escherichia_coli ''E. coli'']
+RcnR is also tetrameric and has the same protein-to-metal stoichiometry. Through a combination of site-directed mutagenesis, lacZ activity assays and X-ray absorption spectroscopy (XAS) structural studies it is now known that RcnR uses a different ligand set to bind Ni(II) than it does Co(II).
+The Ni(II) site is bound by the N-terminal amine, Cys35, and His64. Because the Ni(II) site has an octahedral geometry, there are three metal binding residues whose identity is unknown. However, using XAS and lacZ activity assays it is known that the remaining ligands bind to the Ni(II) using N/O atoms and that there is a total of two histidine ligand bound to the Ni(II), leaving the identity of one unaccounted for. Studies have shown that this histidine is not His3, His60, or His67.
+The Co(II) site is bound the the N-terminal amine, His3, Cys35, His64 and possibly His60. The Co(II) site of RcnR also has an octahedral geometry, leaving 1-2 residues whose identity is unknown. XAS reveals that these ligands are bound to Co(II) using N/O atoms and that there are a total of three histidine ligands bound to the Co(II). Studies have shown that His67 is not a Co(II) ligand.
 == Research Interests ==