title: Spectroscopic and electrochemical studies on structural change of plastocyanin and its tyrosine 83 mutants induced by interaction with lysine peptides.
abstract: Interactions of wild-type and Tyr83 mutant (Y83F, Y83S, Y83L, and Y83H) plastocyanins (PCs) with lysine peptides as models for the PC interacting site of cytochrome f have been studied by absorption, resonance Raman, and electron paramagnetic resonance (EPR) spectroscopies and electrochemical measurements. The spectral and electrochemical properties of PCs corresponded well with each other; species having a longer wavelength maximum for the S(Cys) pi --> Cu 3d(x)()()2(-)(y)()()2 charge transfer (CT) band observed around 600 nm and a stronger intensity for the 460-nm absorption band exhibited stronger intensities for the positive Met --> Cu 3d(x)()()2(-)(y)()()2 and negative His pi(1) --> Cu 3d(x)()()2(-)(y)()()2 circular dichroism (CD) bands at about 420 and 470 nm, respectively, a lower average nu(Cu)(-)(S) frequency, a smaller |A( parallel)| EPR parameter, and a higher redox potential, properties all related to a weaker Cu-S(Cys) bond and a more tetrahedral planar geometry for the Cu site. Similarly, on oligolysine binding to wild-type and several Tyr83 mutant PCs, a longer absorption maximum for the 600-nm CT band, a stronger intensity for the 460-nm absorption band, stronger 420-nm positive and 470-nm negative CD bands, and a lower average nu(Cu)(-)(S) frequency were observed, suggesting that PC assumes a slight more tetrahedral geometry on binding of oligolysine. Since changes were observed for both wild-type and Tyr83 mutant PCs, the structural change due to binding of oligolysine to PC may not be transmitted through the path of Tyr83-Cys84-copper by a cation-pi interaction which is proposed for electron transfer.
authors.affiliation: Department of Chemistry, Graduate School of Science, and Research Center for Materials Science, Nagoya University, Japan. k46230a@nucc.cc.nagoya-u.ac.jp
authors.forename: S
authors.initials: S
authors.lastname: Hirota
authors.forename: K
authors.initials: K
authors.lastname: Hayamizu
authors.forename: T
authors.initials: T
authors.lastname: Okuno
authors.forename: M
authors.initials: M
authors.lastname: Kishi
authors.forename: H
authors.initials: H
authors.lastname: Iwasaki
authors.forename: T
authors.initials: T
authors.lastname: Kondo
authors.forename: T
authors.initials: T
authors.lastname: Hibino
authors.forename: T
authors.initials: T
authors.lastname: Takabe
authors.forename: T
authors.initials: T
authors.lastname: Kohzuma
authors.forename: O
authors.initials: O
authors.lastname: Yamauchi
mesh_terms: D019943:Amino Acid Substitution; D017931:DNA Primers; D004563:Electrochemistry; D004578:Electron Spin Resonance Spectroscopy; D008239:Lysine; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D010970:Plastocyanin / Q000737:chemistry* / Q000378:metabolism; D016133:Polymerase Chain Reaction; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D013053:Spectrophotometry; D013059:Spectrum Analysis, Raman; D014443:Tyrosine
chemical_list: D017931:DNA Primers; D011994:Recombinant Proteins; D014443:Tyrosine; D010970:Plastocyanin; D008239:Lysine