title: Mavicyanin, a blue copper protein from Cucurbita pepo medullosa. Purification and characterization.
abstract: 1. The copper protein mavicyanin has been isolated and purified from the green squash Cucurbita pepo medullosa. 2. Mavicyanin contains one type-1 copper/18000 Mr, which can be characterized by: intense absorption maximum at 600 nm (epsilon = 5000 M-1 cm-1/Cu, A280/A600 = 8.0 +/- 0.5, A600/A403 = 7.0 +/- 0.25, maximum of fluorescence emission at 335 nM. 3. In the oxidized state the copper of mavicyanin is 100% detectable by electron paramagnetic resonance (EPR). Computer simulation of the rhombic EPR signal gives gz = 2.287, gy = 2.077, gx = 2.025, Az = 3.5 mT, Ay = 2.9 mT and Ax = 5.7 mT. 4. Like other simple type-1 copper proteins, such as stellacyanin, azurin or plastocyanin, mavicyanin is readily reduced by hydroquinone or L-ascorbic acid. Its midpoint potential E'm was determined to be + 285 mV. The reduced protein reacts rather slowly with dioxygen, but is rapidly reoxidized by ferricyanide.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D003300:Copper / Q000032:analysis*; D004578:Electron Spin Resonance Spectroscopy; D005292:Ferricyanides; D008667:Metalloproteins / Q000302:isolation & purification; D010084:Oxidation-Reduction; D010940:Plant Proteins / Q000302:isolation & purification; D010944:Plants / Q000032:analysis; D011487:Protein Conformation; D013050:Spectrometry, Fluorescence; D013053:Spectrophotometry
chemical_list: D000596:Amino Acids; D005292:Ferricyanides; D008667:Metalloproteins; D010940:Plant Proteins; C022828:mavicyanin protein, Cucurbita pepo; D003300:Copper