title: New Type 2 Copper-Cysteinate Proteins. Copper Site Histidine-to-Cysteine Mutants of Yeast Copper-Zinc Superoxide Dismutase.
abstract: Preparation and characterization of two new site-directed mutant copper-zinc superoxide dismutase proteins from Saccharomyces cerevisiae, i.e., His46Cys (H46C) and His120Cys (H120C), in which individual histidyl ligands in the copper-binding site were replaced by cysteine, are reported here. These two mutant CuZnSOD proteins may be described as type 2 (or normal) rather than type 1 (or blue) copper-cysteinate proteins and are characterized by their yellow rather than blue color, resulting from intense copper-to-sulfur charge transfer bands around 400 nm, their type 2 EPR spectra, with large rather than small nuclear hyperfine interactions, and their characteristic type 2 d-d electronic absorption spectra. An interesting difference between these two copper site His-to-Cys mutations is that the imidazolate bridge between the two metal sites that is characteristic of the wild-type protein remains intact in the case of the H46C mutant but is not present in the case of the H120C mutant.
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095, Department of Molecular Pharmacology, Albert Einstein College of Medicine of Yeshiva University, Bronx, New York 10461, Department of Chemistry and Biochemistry, Loyola Marymount University, Los Angeles, California 90045, and Department of Chemistry, University of Florence, Florence, Italy.
authors.forename: Yi
authors.initials: Y
authors.lastname: Lu
authors.forename: James A.
authors.initials: JA
authors.lastname: Roe
authors.forename: Christopher J.
authors.initials: CJ
authors.lastname: Bender
authors.forename: Jack
authors.initials: J
authors.lastname: Peisach
authors.forename: Lucia
authors.initials: L
authors.lastname: Banci
authors.forename: Ivano
authors.initials: I
authors.lastname: Bertini
authors.forename: Edith B.
authors.initials: EB
authors.lastname: Gralla
authors.forename: Joan Selverstone
authors.initials: JS
authors.lastname: Valentine