Open AccessFurther perspectives on the charge transfer transitions of blue copper proteins and the ligand moieties in stellacyanin
Author(s) -
David R. McMillin,
Margaret C. Morris
Publication year - 1981
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.78.11.6567
Subject(s) - azurin , plastocyanin , copper protein , chemistry , cystine , cysteine , crystallography , ligand (biochemistry) , methionine , copper , thiol , photochemistry , chemical physics , electron transfer , amino acid , biochemistry , photosystem i , receptor , chloroplast , organic chemistry , gene , enzyme
The charge transfer spectra of plastocyanin and azurin are analyzed in detail, taking into account the structural information that is available. The number and relative energies of the low-lying charge transfer bands attributable to cysteine and methionine sulfur are considered with reference to the energy levels associated with the donor centers and to experimental work on relevant complexes. Two cysteine → Cu(II) charge transfer transitions are assigned to bands that occur near 620 nm and near 770 nm. Energy considerations suggest that the methionine → Cu(II) transition occurs in the vicinity of 550 nm for both plastocyanin and azurin. The existence of a disulfide linkage in stellacyanin is established by thiol titrations, and the possibility exists that the fourth ligand in stellacyanin may involve disulfide sulfur. If so, the cystine → Cu(II) transition is also expected to appear around 550 nm.