title: Properties of Paracoccus denitrificans amicyanin.
abstract: Paracoccus denitrificans synthesizes an inducible, periplasmic, blue copper protein [Husain, M., & Davidson, V.L. (1985) J. Biol. Chem. 260, 14626-14629] that can be classified as an amicyanin on the basis of its ability to accept electrons from methylamine dehydrogenase. The amino acid composition and sequence of the 10 N-terminal residues of this protein have been determined. From these data, it is evident that amicyanin is structurally distinct from azurins as it contains no disulfide bond and an N-terminal sequence that is completely different from the highly conserved N-terminal azurin sequences. Dialysis of reduced amicyanin against potassium cyanide resulted in a nearly quantitative yield of apoamicyanin. Amicyanin and apoamicyanin exhibit fluorescence emission maxima at 314 nm when excited at 280 nm. Addition of 6 M guanidine hydrochloride shifts these emission maxima to 350 nm. The fluorescence intensity of apoamicyanin is 10-fold greater than that of amicyanin. Addition of copper to the apoprotein caused a stoichiometric quenching of fluorescence and restoration of visible absorbance with no concomitant change in absorbance at 280 nm. At least one cysteine residue, which reacts with 5,5'-dithiobis(2-nitrobenzoic acid) in apoamicyanin, does not react in the holoprotein, even in the presence of 6 M guanidine hydrochloride. Reductive and oxidative titrations of amicyanin indicate that it is a one-electron carrier. This amicyanin is also able to accept electrons from the methylamine dehydrogenase isolated from bacterium W3A1, which is taxonomically very different from P. denitrificans.
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D003300:Copper / Q000378:metabolism; D019327:Copper Sulfate; D004227:Dithionite / Q000494:pharmacology; D004228:Dithionitrobenzoic Acid / Q000494:pharmacology; D007700:Kinetics; D008667:Metalloproteins / Q000302:isolation & purification* / Q000378:metabolism; D010231:Paracoccus denitrificans / Q000378:metabolism*; D010446:Peptide Fragments / Q000032:analysis; D013050:Spectrometry, Fluorescence
chemical_list: D001426:Bacterial Proteins; D008667:Metalloproteins; D010446:Peptide Fragments; C017079:mauC protein, Methylobacterium extorquens; D004227:Dithionite; D003300:Copper; D004228:Dithionitrobenzoic Acid; D019327:Copper Sulfate