Structures of complexes of octahaem cytochrome c nitrite reductase from Thioalkalivibrio nitratireducens with sulfite and cyanide.
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Trofimov AA, Polyakov KM, Boyko KM, Tikhonova TV, Safonova TN, Tikhonov AV, Popov AN, Popov VO
Structures of complexes of octahaem cytochrome c nitrite reductase from Thioalkalivibrio nitratireducens with sulfite and cyanide.
Acta Crystallogr D Biol Crystallogr. 2010 Oct;66(Pt 10):1043-7. doi: 10.1107/S0907444910031665. Epub 2010 Sep 18.
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- Abstract
The structures of complexes of octahaem cytochrome c nitrite reductase from the bacterium Thioalkalivibrio nitratireducens (TvNiR) with the substrate sulfite (1.4 A resolution; R(cryst) = 0.126) and the inhibitor cyanide (1.55 A resolution; R(cryst) = 0.148) have been established. The complex with sulfite was prepared by the reduction of the protein crystal with sodium dithionite. The sulfite ion is bound to the iron ion of the catalytic haem through the S atom. The Fe-S distance is 2.24 A. The structure of the cyanide complex with full occupancy of the ligand site was established for the first time for cytochrome c nitrite reductases. The cyanide ion is bound to the catalytic haem iron through the C atom. The Fe-C distance is 1.91 A and the Fe-C-N angle is 171 degrees . The sulfite reductase activity of TvNiR was measured at different pH values. The activity is 0.02 micromol of HS(-) per minute per milligram at pH 7.0; it decreases with increasing pH and is absent at pH 9.0.