4rwm | pdb_00004rwm
Kuenenia stuttgartiensis hydroxylamine oxidoreductase cryoprotected with ethylene glycol
Structural highlights
FunctionHAO_KUEST Catalyzes the oxidation of hydroxylamine to nitric oxide with cytochrome c acting as an electron acceptor (PubMed:21964329, PubMed:24302732). Does not oxidize hydroxylamine to nitrite (PubMed:24302732). Also able to catalyze the four-electron oxidation of hydrazine to N(2) in vitro with reduced efficiency; however, this reaction is probably not physiological (PubMed:21964329, PubMed:24302732).[1] [2] Publication Abstract from PubMedHydroxylamine oxidoreductases (HAOs) contain a unique haem cofactor called P460 that consists of a profoundly ruffled c-type haem with two covalent bonds between the haem porphyrin and a conserved tyrosine. This cofactor is exceptional in that it abstracts electrons from a ligand bound to the haem iron, whereas other haems involved in redox chemistry usually inject electrons into their ligands. The effects of the tyrosine cross-links and of the haem ruffling on the chemistry of this cofactor have been investigated theoretically but are not yet clear. A new crystal structure of an HAO from Candidatus Kuenenia stuttgartiensis, a model organism for anaerobic ammonium oxidation, now shows that its P460 cofactor has yet another unexpected reactivity: when ethylene glycol was used as a cryoprotectant, the 1.8 A resolution electron-density maps showed additional density which could be interpreted as an ethylene glycol molecule covalently bound to the C16 atom of the haem ring, opposite the covalent links to the conserved tyrosine. Possible causes for this unexpected reactivity are discussed. An unexpected reactivity of the P460 cofactor in hydroxylamine oxidoreductase.,Dietl A, Maalcke W, Barends TR Acta Crystallogr D Biol Crystallogr. 2015 Aug;71(Pt 8):1708-13. doi:, 10.1107/S1399004715010706. Epub 2015 Jul 31. PMID:26249351[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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