Article

Genomic DNA cloning of the region encoding nitric oxide reductase in Paracoccus halodenitrificans and a structure model relevant to cytochrome oxidase.

Institute for Molecular Science, Okazaki National Research Institutes, Okazaki, Japan.
Biochemical and Biophysical Research Communications (impact factor: 2.48). 03/1998; 243(2):400-6. DOI:10.1006/bbrc.1998.8106 pp.400-6
Source: PubMed

ABSTRACT The structural genes for the NO reductase in Paracoccus halodenitrificans, norC, norB, and norQ were sequenced. The norC and norB encode the cytochrome c (NorC) and cytochrome b (NorB) subunits, respectively. The matured NorC (17,258 Da, 148 residues) has a binding motif (CXYCH) for heme c, which is axially coordinated by His65 and Met115. NorB (52,337 Da, 451 residues) has twelve putative transmembrane helices and the 19% sequence homology with the subunit I of cytochrome oxidase from Paracoccus denitrificans. Several histidine and glutamate residues were identified as the ligands for two hemes b and a non-heme iron in comparison with the sequence of cytochrome oxidase. The higher-order model structures constructed from the amino acid sequences of NorC and NorB showed the topology of the helical segments and the locations of the metal centers.

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    Article: Roles of glutamates and metal ions in a rationally designed nitric oxide reductase based on myoglobin.
    Ying-Wu Lin, Natasha Yeung, Yi-Gui Gao, Kyle D Miner, Shiliang Tian, Howard Robinson, Yi Lu
    [show abstract] [hide abstract]
    ABSTRACT: A structural and functional model of bacterial nitric oxide reductase (NOR) has been designed by introducing two glutamates (Glu) and three histidines (His) in sperm whale myoglobin. X-ray structural data indicate that the three His and one Glu (V68E) residues bind iron, mimicking the putative Fe(B) site in NOR, while the second Glu (I107E) interacts with a water molecule and forms a hydrogen bonding network in the designed protein. Unlike the first Glu (V68E), which lowered the heme reduction potential by approximately 110 mV, the second Glu has little effect on the heme potential, suggesting that the negatively charged Glu has a different role in redox tuning. More importantly, introducing the second Glu resulted in a approximately 100% increase in NOR activity, suggesting the importance of a hydrogen bonding network in facilitating proton delivery during NOR reactivity. In addition, EPR and X-ray structural studies indicate that the designed protein binds iron, copper, or zinc in the Fe(B) site, each with different effects on the structures and NOR activities, suggesting that both redox activity and an intermediate five-coordinate heme-NO species are important for high NOR activity. The designed protein offers an excellent model for NOR and demonstrates the power of using designed proteins as a simpler and more well-defined system to address important chemical and biological issues.
    Proceedings of the National Academy of Sciences 05/2010; 107(19):8581-6. · 9.68 Impact Factor
Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. The impact factor represents a rough estimation of the journal's impact factor and does not reflect the actual current impact factor. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.

Keywords

19% sequence homology
 
amino acid sequences
 
binding motif
 
CXYCH
 
cytochrome b
 
cytochrome c
 
cytochrome oxidase
 
glutamate residues
 
helical segments
 
hemes b
 
higher-order model structures
 
locations
 
matured NorC
 
metal centers
 
norB encode
 
norC
 
Paracoccus denitrificans
 
Paracoccus halodenitrificans
 
structural genes
 
topology
 

N Sakurai