Stellacyanin is a protein specific to plants that contains a singular copper ion bound in a blue configuration (type 1). Stellacyanin’s spectroscopic properties help us differentiate it from plastocyanin, which is another monocopper blue protein found in plants. [1]


Stellacyanins are characterized by their uniquely low redox potentials, as low as +180 mv and reach up to 280 mV. Other blue copper protein redox potentials start around 310 mV and reach up to 680 mV. [1]

A mutant cucumber stellacyanin was created by replacing the glutamine axial ligand (a ligand which all other blue proteins contain) with a methionine (Q99M) and purified. The spectroscopic properties found were common to uclacyanin- not plantacyanins. Stellacyanin with the substation of the axial G redox potential was calculated to be +420 mV, which much higher than the redox potential of the stellacyanin found in nature (without methionine) at +260 mV. Structural design also poses the question if stellacyanins may possibly not be diffusible electron transfer proteins in long range electron-transfering. Stellacyanins are most involved in redox reactions of plants that take place during a defense response, and formation of lignin.[1]

Stellacyanins are also distinguishable from plantacyanins and other cupredoxins by the structure if their amino acid residue position relative to the pivotal site of copper.[1]

3D structure of Stellacyanin

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References

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  1. ^ a b c d e Nersissian Ma, A.M.; Immoos, C.; Hill, M.G.; Hart, P.J.; Williams, G.; Herrmann, R.G.; Valentine, J.S. Uclacyanins, stellacyanins, and plantacyanins are distinct subfamilies of phytocyanins: Plant-specific mononuclear blue copper proteins. Protein Sci. 1998, 7, 1915–1929