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pubmed:abstractText |
We have determined the 1.8 A X-ray crystal structure of a monoheme c-type cytochrome, cytochrome P460, from Nitrosomonas europea. The chromophore possesses unusual spectral properties analogous to those of the catalytic heme P460 of hydroxylamine oxidoreductase (HAO), the only known heme in biology to withdraw electrons from an iron-coordinated substrate. The analysis reveals a homodimeric structure and elucidates a new c-type cytochrome fold that is predominantly beta-sheet. In addition to the two cysteine thioether links to the porphyrin typical of c-type hemes, there is a third proteinaceous link involving a conserved lysine. The covalent bond is between the lysine side-chain nitrogen and the 13'-meso carbon of the heme, which, following cross-link formation, is sp3-hybridized, demonstrating the loss of conjugation at this position within the porphyrin. The structure has implications for the analogous tyrosine-heme meso carbon cross-link observed in HAO.
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pubmed:affiliation |
Department of Biochemistry, Molecular Biology and Biophysics, The University of Minnesota, Minneapolis, Minnesota 55455, USA.
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pubmed:publicationType |
Journal Article,
Research Support, U.S. Gov't, Non-P.H.S.,
Research Support, Non-U.S. Gov't,
Research Support, N.I.H., Extramural
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