1. Structural study of the X-ray-induced enzymatic reaction of octahaem cytochrome C nitrite reductase.
- Author
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Trofimov AA, Polyakov KM, Lazarenko VA, Popov AN, Tikhonova TV, Tikhonov AV, and Popov VO
- Subjects
- Catalytic Domain, Crystallography, X-Ray, Cytochromes a1 radiation effects, Cytochromes c1 radiation effects, Ectothiorhodospiraceae radiation effects, Models, Molecular, Nitrate Reductases radiation effects, Nitrites chemistry, Nitrites radiation effects, Protein Binding, Radiation Effects, Substrate Specificity, Sulfites chemistry, Sulfites radiation effects, X-Rays, Cytochromes a1 chemistry, Cytochromes a1 metabolism, Cytochromes c1 chemistry, Cytochromes c1 metabolism, Ectothiorhodospiraceae enzymology, Heme chemistry, Nitrate Reductases chemistry, Nitrate Reductases metabolism, Nitrites metabolism, Protein Conformation radiation effects, Sulfites metabolism
- Abstract
Octahaem cytochrome c nitrite reductase from the bacterium Thioalkalivibrio nitratireducens catalyzes the reduction of nitrite to ammonium and of sulfite to sulfide. The reducing properties of X-ray radiation and the high quality of the enzyme crystals allow study of the catalytic reaction of cytochrome c nitrite reductase directly in a crystal of the enzyme, with the reaction being induced by X-rays. Series of diffraction data sets with increasing absorbed dose were collected from crystals of the free form of the enzyme and its complexes with nitrite and sulfite. The corresponding structures revealed gradual changes associated with the reduction of the catalytic haems by X-rays. In the case of the nitrite complex the conversion of the nitrite ions bound in the active sites to NO species was observed, which is the beginning of the catalytic reaction. For the free form, an increase in the distance between the oxygen ligand bound to the catalytic haem and the iron ion of the haem took place. In the case of the sulfite complex no enzymatic reaction was detected, but there were changes in the arrangement of the active-site water molecules that were presumably associated with a change in the protonation state of the sulfite ions. more...
- Published
- 2015
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