2noo
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Crystal Structure of Mutant NikA
OverviewOverview
Intracellular nickel is required by Escherichia coli as a cofactor for a, number of enzymes and is necessary for anaerobic respiration. However, high concentrations of nickel are toxic, so both import and export systems, have evolved to control the cellular level of the metal. The nik operon in, E. coli encodes a nickel-uptake system that includes the periplasmic, nickel-binding protein NikA. The crystal structures of wild-type NikA both, bound to nickel and in the apo form have been solved previously. The, liganded structure appeared to show an unusual interaction between the, nickel and the protein in which no direct bonds are formed. The highly, unusual nickel coordination suggested by the crystal structure contrasted, strongly with earlier X-ray spectroscopic studies. The known, nickel-binding site has been probed by extensive mutagenesis and, isothermal titration calorimetry and it has been found that even large, numbers of disruptive mutations appear to have little effect on the nickel, affinity. The crystal structure of a binding-site mutant with nickel bound, has been solved and it is found that nickel is bound to two histidine, residues at a position distant from the previously characterized binding, site. This novel site immediately resolves the conflict between the, crystal structures and other biophysical analyses. The physiological, relevance of the two binding sites is discussed.
About this StructureAbout this Structure
2NOO is a Single protein structure of sequence from Escherichia coli with IOD and NI as ligands. Active as Nickel-transporting ATPase, with EC number 3.6.3.24 Full crystallographic information is available from OCA.
ReferenceReference
Nickel binding to NikA: an additional binding site reconciles spectroscopy, calorimetry and crystallography., Addy C, Ohara M, Kawai F, Kidera A, Ikeguchi M, Fuchigami S, Osawa M, Shimada I, Park SY, Tame JR, Heddle JG, Acta Crystallogr D Biol Crystallogr. 2007 Feb;63(Pt 2):221-9. Epub 2007, Jan 16. PMID:17242515
Page seeded by OCA on Wed Nov 21 12:48:58 2007