3uu9 | pdb_00003uu9

Structure of the free TvNiRb form of Thioalkalivibrio nitratireducens cytochrome c nitrite reductase

spinqualitylabelsall models 3uu9, resolution 2.20Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 3uu9 is a 2 chain structure with sequence from Thioalkalivibrio nitratireducens. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: CA, HEC, NA, PG4 Related: 3lgq, 3rkh Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function [Q5F2I3_9GAMM] Plays a role in nitrite reduction (By similarity).[SAAS:SAAS003321_004_001592] Publication Abstract from PubMed Octahaem cytochrome c nitrite reductase from Thioalkalivibrio nitratireducens (TvNiR), like the previously characterized pentahaem nitrite reductases (NrfAs), catalyzes the six-electron reductions of nitrite to ammonia and of sulfite to sulfide. The active site of both TvNiR and NrfAs is formed by the lysine-coordinated haem and His, Tyr and Arg residues. The distinguishing structural feature of TvNiR is the presence of a covalent bond between the CE2 atom of the catalytic Tyr303 and the S atom of Cys305, which might be responsible for the higher nitrite reductase activity of TvNiR compared with NrfAs. In the present study, a new modified form of the enzyme (TvNiRb) that contains an additional covalent bond between Tyr303 CE1 and Gln360 CG is reported. Structures of TvNiRb in complexes with phosphate (1.45 A resolution) and sulfite (1.8 A resolution), the structure of TvNiR in a complex with nitrite (1.83 A resolution) and several additional structures were determined. The formation of the second covalent bond by Tyr303 leads to a decrease in both the nitrite and sulfite reductase activities of the enzyme. Tyr303 is located at the exit from the putative proton-transport channel to the active site, which is absent in NrfAs. This is an additional argument in favour of the involvement of Tyr303 as a proton donor in catalysis. The changes in the activity of cytochrome c nitrite reductases owing to the formation of Tyr-Cys and Tyr-Gln bonds may be associated with changes in the pK(a) value of the catalytic tyrosine. Covalent modifications of the catalytic tyrosine in octahaem cytochrome c nitrite reductase and their effect on the enzyme activity.,Trofimov AA, Polyakov KM, Tikhonova TV, Tikhonov AV, Safonova TN, Boyko KM, Dorovatovskii PV, Popov VO Acta Crystallogr D Biol Crystallogr. 2012 Feb;68(Pt 2):144-53. Epub 2012, Jan 13. PMID:22281743 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Cytochrome c nitrite reductase

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