PMID:9325288
Citation |
Magalon, A, Lemesle-Meunier, D, Rothery, RA, Frixon, C, Weiner, JH and Blasco, F (1997) Heme axial ligation by the highly conserved His residues in helix II of cytochrome b (NarI) of Escherichia coli nitrate reductase A. J. Biol. Chem. 272:25652-8 |
---|---|
Abstract |
Optical spectroscopy and EPR studies confirm the existence of two b-type hemes in the NarI subunit (cytochrome bnr) of the membrane-bound nitrate reductase (NarGHI) of Escherichia coli. Replacement of His-56 by Arg and His-66 by Tyr results in the loss of the high-potential heme and of the low-potential heme, respectively. These data support the assignment of the axial ligands to the low-potential heme (His-66 and His-187) and to the high-potential heme (His-56 and His-205). This pairing is consistent with the model proposed for NarI of the nitrate reductase of Thiosphaera pantotropha (Berks, B. C., Page, M. D., Richardson, D. J. , Reilly, A., Cavill, A., Outen, F., and Ferguson, S. J. (1995) Mol. Microbiol. 15, 319-331) in which the two bis-histidine ligated hemes are coordinated by conserved His residues of helix II and V. EPR and optical studies suggest that the low-potential heme (Em,7 = +17 mV) and the high-potential heme (Em,7 = +122 mV) are located near the periplasmic side and the cytoplasmic side of the membrane, respectively. Moreover, correct insertion of both hemes into NarI requires anchoring to NarGH. |
Links | |
Keywords |
Cold Temperature; Conserved Sequence; Cytochrome b Group/genetics; Cytochrome b Group/metabolism; Dimerization; Electron Spin Resonance Spectroscopy; Escherichia coli/enzymology; Heme/metabolism; Histidine/metabolism; Mutagenesis, Site-Directed; Nitrate Reductase; Nitrate Reductases/metabolism; Potentiometry; Protein Structure, Secondary; Spectrophotometry, Atomic |
edit table |
Significance
You can help EcoliWiki by summarizing why this paper is useful
Useful Materials and Methods
You can help Ecoliwiki by describing the useful materials (strains, plasmids, antibodies, etc) described in this paper.
Annotations
<annotationlinks/>
EcoliWiki Links
Add links to pages that link here (e.g. gene, product, method pages)
References
See Help:References for how to manage references in EcoliWiki.