Kinetics and Mechanism of Redox-Coupled, Long-Range Proton Transfer in an Iron−Sulfur Protein. Investigation by Fast-Scan Protein-Film Voltammetry

1998 ◽  
Vol 120 (28) ◽  
pp. 7085-7094 ◽  
Author(s):  
Judy Hirst ◽  
Jillian L. C. Duff ◽  
Guy N. L. Jameson ◽  
Mary A. Kemper ◽  
Barbara K. Burgess ◽  
...  
Keyword(s):  
Proton Transfer ◽  
Long Range ◽  
Kinetics And Mechanism ◽  
Protein Film ◽  
Protein Film Voltammetry ◽  
Iron Sulfur ◽  
Sulfur Protein ◽  
Iron Sulfur Protein

scholarly journals Gene Cluster of Rhodothermus marinusHigh-Potential Iron-Sulfur Protein:Oxygen Oxidoreductase, acaa3-Type Oxidase Belonging to the Superfamily of Heme-Copper Oxidases

2001 ◽  
Vol 183 (2) ◽  
pp. 687-699 ◽  
Author(s):  
Margarida Santana ◽  
Manuela M. Pereira ◽  
Nuno P. Elias ◽  
Cláudio M. Soares ◽  
Miguel Teixeira
Keyword(s):  
Proton Transfer ◽  
Electron Donor ◽  
Structural Model ◽  
Paracoccus Denitrificans ◽  
Hydroxyl Group ◽  
Rhodothermus Marinus ◽  
Iron Sulfur ◽  
Sulfur Protein ◽  
Iron Sulfur Protein ◽  
Heme Copper Oxidases

ABSTRACT The respiratory chain of the thermohalophilic bacteriumRhodothermus marinus contains an oxygen reductase, which uses HiPIP (high potential iron-sulfur protein) as an electron donor. The structural genes encoding the four subunits of this HiPIP:oxygen oxidoreductase were cloned and sequenced. The genes for subunits II, I, III, and IV (named rcoxA to rcoxD) are found in this order and seemed to be organized in an operon of at least five genes with a terminator structure a few nucleotides downstream ofrcoxD. Examination of the amino acid sequence of the Rcox subunits shows that the subunits of the R. marinus enzyme have homology to the corresponding subunits of oxidases belonging to the superfamily of heme-copper oxidases. RcoxB has the conserved histidines involved in binding the binuclear center and the low-spin heme. All of the residues proposed to be involved in proton transfer channels are conserved, with the exception of the key glutamate residue of the D-channel (E278, Paracoccus denitrificans numbering). Analysis of the homology-derived structural model of subunit I shows that the phenol group of a tyrosine (Y) residue and the hydroxyl group of the following serine (S) may functionally substitute the glutamate carboxyl in proton transfer. RcoxA has an additional sequence for heme C binding, after the CuA domain, that is characteristic ofcaa 3 oxidases belonging to the superfamily. Homology modeling of the structure of this cytochrome domain of subunit II shows no marked electrostatic character, especially around the heme edge region, suggesting that the interaction with a redox partner is not of an electrostatic nature. This observation is analyzed in relation to the electron donor for this caa 3oxidase, the HiPIP. In conclusion, it is shown that an oxidase, which uses an iron-sulfur protein as an electron donor, is structurally related to the caa 3 class of heme-copper cytochrome c oxidases. The data are discussed in the framework of the evolution of oxidases within the superfamily of heme-copper oxidases.

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