1siw
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Crystal structure of the apomolybdo-NarGHI
OverviewOverview
We have used EPR spectroscopy, redox potentiometry, and protein, crystallography to characterize the [4Fe-4S] cluster (FS0) of the, Escherichia coli nitrate reductase A (NarGHI) catalytic subunit (NarG)., FS0 is clearly visible in the crystal structure of NarGHI [Bertero, M. G., et al. (2003) Nat. Struct. Biol. 10, 681-687] but has novel coordination, comprising one His residue and three Cys residues. At low temperatures, (<15 K), reduced NarGHI exhibits a previously unobserved EPR signal, comprising peaks at g = 5.023 and g = 5.556. We have assigned these, features to a [4Fe-4S](+) cluster with an S = (3)/(2) ground state, with, the g = 5.023 and g = 5.556 peaks corresponding to subpopulations, exhibiting DeltaS = (1)/(2) and DeltaS = (3)/(2) transitions, respectively. Both peaks exhibit midpoint potentials of approximately -55, mV at pH 8.0 and are eliminated in the EPR spectrum of apomolybdo-NarGHI., The structure of apomolybdo-NarGHI reveals that FS0 is still present but, that there is significant conformational disorder in a segment of residues, that includes one of the Cys ligands. On the basis of these observations, we have assigned the high-spin EPR features of reduced NarGHI to FS0.
About this StructureAbout this Structure
1SIW is a Protein complex structure of sequences from Escherichia coli with GDP, HEM, SF4, F3S and 3PH as ligands. Active as Nitrate reductase, with EC number 1.7.99.4 Full crystallographic information is available from OCA.
ReferenceReference
The catalytic subunit of Escherichia coli nitrate reductase A contains a novel [4Fe-4S] cluster with a high-spin ground state., Rothery RA, Bertero MG, Cammack R, Palak M, Blasco F, Strynadka NC, Weiner JH, Biochemistry. 2004 May 11;43(18):5324-33. PMID:15122898
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