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Biochim Biophys Acta. 1997 Dec 5;1343(2):144-51.

Cytochromes c-552 from two strains of the hydrogenotrophic bacterium Alcaligenes eutrophus are sequence homologs of the cytochromes c8 from the denitrifying pseudomonads.

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Department of Biochemistry, Physiology and Microbiology, University of Gent, Belgium.


Soluble cytochromes c-552 were purified from two strains of the hydrogenothrophic species Alcaligenes eutrophus and their amino acid sequences determined. The two cytochromes were found to have 5 differences out of a total of 89 residues. The proteins are clearly related to the cytochromes c8 (formerly called Pseudomonas cytochromes c-551), but require a single residue insertion after the methionine sixth heme ligand relative to the Pseudomonas aeruginosa protein. The consensus residues Trp56 and Trp77, characteristic for the c8 family, are also present in the Alcaligenes proteins. Overall, the Alcaligenes cytochromes are only 43% identical to the Pseudomonas proteins which average 68% identity to one another. They are also only 45% identical to cytochrome c8 from Hydrogenobacter thermophilus, another hydrogenothrophic species, which indicates that the hydrogen utilizing bacteria are not more closely related to one another than they are to other species. The finding of cytochrome c8 in Alcaligenes eutrophus completes the recent characterization of a cytochrome cd1-nitrite reductase from this bacterial species and suggests the existence of the same denitrification pathway as in Pseudomonas where these two proteins are reaction partners.

[Indexed for MEDLINE]

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