title: Why do proteins use selenocysteine instead of cysteine?
abstract: Selenocysteine is present in a variety of proteins and catalyzes the oxidation of thiols to disulfides and the reduction of disulfides to thiols. Here, we compare the kinetic and thermodynamic properties of cysteine with its selenium-containing analogon, selenocysteine. Reactions of simple selenols at pH 7 are up to four orders of magnitude faster than their sulfur analogs, depending on reaction type. In redox-related proteins, the use of selenium instead of sulfur can be used to tune electrode, or redox, potentials. Selenocysteine could also have a protective effect in proteins because its one-electron oxidized product, the selanyl radical, is not oxidizing enough to modify or destroy proteins, whereas the cysteine-thiyl radical can do this very rapidly.
authors.affiliation: Laboratorium für Anorganische Chemie, Departement Chemie und Angewandte Biowissenschaften, ETH-Zürich, Wolfgang-Pauli-Strasse 10, 8093, Zürich, Switzerland. nauser@inorg.chem.ethz.ch
authors.forename: Thomas
authors.initials: T
authors.lastname: Nauser
authors.forename: Daniel
authors.initials: D
authors.lastname: Steinmann
authors.forename: Willem H
authors.initials: WH
authors.lastname: Koppenol
mesh_terms: D003545:Cysteine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism*; D007700:Kinetics; D010084:Oxidation-Reduction; D011506:Proteins / Q000737:chemistry* / Q000378:metabolism*; D012643:Selenium / Q000737:chemistry / Q000378:metabolism; D018036:Selenium Compounds / Q000737:chemistry / Q000378:metabolism; D013455:Sulfur / Q000737:chemistry / Q000378:metabolism; D013816:Thermodynamics
chemical_list: D011506:Proteins; D018036:Selenium Compounds; C442270:selenol; D013455:Sulfur; D012643:Selenium; D003545:Cysteine