title: Redox chemistry of the Schizosaccharomyces pombe ferredoxin electron-transfer domain and influence of Cys to Ser substitutions.
abstract: Schizosaccharomyces pombe (Sp) ferredoxin contains a C-terminal electron transfer protein ferredoxin domain (etp(Fd)) that is homologous to adrenodoxin. The ferredoxin has been characterized by spectroelectrochemical methods, and Mössbauer, UV-Vis and circular dichroism spectroscopies. The Mössbauer spectrum is consistent with a standard diferric [2Fe-2S](2+) cluster. While showing sequence homology to vertebrate ferredoxins, the E°' and the reduction thermodynamics for etp(Fd) (-0.392 V) are similar to plant-type ferredoxins. Relatively stable Cys to Ser derivatives were made for each of the four bound Cys residues and variations in the visible spectrum in the 380-450 nm range were observed that are characteristic of oxygen ligated clusters, including members of the [2Fe-2S] cluster IscU/ISU scaffold proteins. Circular dichroism spectra were similar and consistent with no significant structural change accompanying these mutations. All derivatives were active in an NADPH-Fd reductase cytochrome c assay. The binding affinity of Fd to the reductase was similar, however, V(max) reflecting rate limiting electron transfer was found to decrease ~13-fold. The data are consistent with relatively minor perturbations of both the electronic properties of the cluster following substitution of the Fe-bond S atom with O, and the electronic coupling of the cluster to the protein.
authors.affiliation: Evans Laboratory of Chemistry, Ohio State University, Columbus, OH 43210, USA.
authors.forename: Shu-pao
authors.initials: SP
authors.lastname: Wu
authors.forename: Marzia
authors.initials: M
authors.lastname: Bellei
authors.forename: Sheref S
authors.initials: SS
authors.lastname: Mansy
authors.forename: Gianantonio
authors.initials: G
authors.lastname: Battistuzzi
authors.forename: Marco
authors.initials: M
authors.lastname: Sola
authors.forename: James A
authors.initials: JA
authors.lastname: Cowan
mesh_terms: D019943:Amino Acid Substitution; D002942:Circular Dichroism; D003545:Cysteine / Q000235:genetics*; D005287:Ferredoxin-NADP Reductase / Q000737:chemistry / Q000378:metabolism; D005288:Ferredoxins / Q000737:chemistry* / Q000378:metabolism; D007506:Iron-Sulfur Proteins / Q000737:chemistry / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D009249:NADP / Q000737:chemistry*; D010084:Oxidation-Reduction; D012568:Schizosaccharomyces / Q000737:chemistry* / Q000378:metabolism*; D029702:Schizosaccharomyces pombe Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D012694:Serine / Q000235:genetics*; D013816:Thermodynamics
chemical_list: D005288:Ferredoxins; D007506:Iron-Sulfur Proteins; D029702:Schizosaccharomyces pombe Proteins; D012694:Serine; D009249:NADP; D005287:Ferredoxin-NADP Reductase; D003545:Cysteine