1uiv
Crystal structures of the liganded and unliganded nickel binding protein NikA from Escherichia coli (Nickel liganded form)
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OverviewOverview
Bacteria have evolved a number of tightly controlled import and export, systems to maintain intracellular levels of the essential but potentially, toxic metal nickel. Nickel homeostasis systems include the dedicated, nickel uptake system nik found in Escherichia coli, a member of the ABC, family of transporters, that involves a periplasmic nickel-binding, protein, NikA. This is the initial nickel receptor and mediator of the, chemotactic response away from nickel. We have solved the crystal, structure of NikA protein in the presence and absence of nickel, showing, that it behaves as a "classical" periplasmic binding protein. In contrast, to other binding proteins, however, the ligand remains accessible to the, solvent and is not completely enclosed. No direct bonds are formed between, the metal cation and the protein. The nickel binding site is apolar, quite, unlike any previously characterized protein nickel binding site. Despite, relatively weak binding, NikA is specific for nickel. Using isothermal, titration calorimetry, the dissociation constant for nickel was found to, be approximately 10 microm and that for cobalt was approximately 20 times, higher.
About this StructureAbout this Structure
1UIV is a Single protein structure of sequence from Escherichia coli with NI as ligand. Full crystallographic information is available from OCA.
ReferenceReference
Crystal structures of the liganded and unliganded nickel-binding protein NikA from Escherichia coli., Heddle J, Scott DJ, Unzai S, Park SY, Tame JR, J Biol Chem. 2003 Dec 12;278(50):50322-9. Epub 2003 Sep 5. PMID:12960164
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