Rhus vemicifera stellacyanin

The blue copper protein stellacyanin, with a molecular weight of about 20,000, is obtained from the Japanese lacquer tree Rhus vemicifera. The EPR spectrum is described by roughly axial g and ACu hfs tensors and an unusually small a j value. As shown in Fig. 39 a, only the largest copper hf value A u can be directly determined from the EPR spectrum202. This coupling does not lie along the largest g-principal axis, in contrast to the usual behaviour of square planar copper complexes. 

Stellacyanin from Rhus vemicifera is less well studied. The polypeptide does not contain a methionine residue showing that the ligands of the type 1 site may vary. There is EXAFS evidence for a short Cu—S(Cys) bond,920 while UV, visible and near IR studies confirm similarities with the other blue proteins. It has been suggested that methionine is replaced as a ligand by an —S—S— group. This is based on resonance Raman921 and NMR studies.922... 

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