title: Co2+ binding cysteine and selenocysteine: a DFT study.
abstract: In this paper we report structural and energetic data for cysteine and selenocysteine in the gas phase and the effect of Co(2+) complexation on their properties. Different conformers are analyzed at the DFT/B3LYP level of both bound and unbound species. Geometries, vibrational frequencies, and natural population analysis are reported and used to understand the activity of these species. In particular, we have focused our attention on the role of sulfur and selenium in the metal binding process and on the resulting deprotonation of the thiol and seleniol functions. From the present calculations we are able to explain, both from electronic structure and thermochemical point of views, a metal-induced thiol deprotonation as observed in gas-phase experiments. A similar process is expected in the case of selenocysteine. In fact, cobalt was found to have a preferential affinity with respect to thiolate and selenolate functions. This can be related to the observation that only S and Se are able-in thiolate and selenolate states-to make a partial charge transfer to the cobalt thus forming very stable complexes. Globally, very similar results are found when substituting S with Se, and a very small difference in cobalt binding affinity is found, thus justifying the use of this substitution in X-ray absorption experiments done on biomolecules containing cysteine metal binding pockets.
authors.affiliation: Laboratoire Analyse et Modélisation pour la Biologie et l'Environnement, Université d'Evry Val d'Essonne, UMR 8587 CNRS, Bat Maupertuis, Boulevard F. Mitterrand, 91025 Evry Cedex, France. rspezia@univ-evry.fr
authors.forename: Riccardo
authors.initials: R
authors.lastname: Spezia
authors.forename: Guewen
authors.initials: G
authors.lastname: Tournois
authors.forename: Thierry
authors.initials: T
authors.lastname: Cartailler
authors.forename: Jeanine
authors.initials: J
authors.lastname: Tortajada
authors.forename: Yannick
authors.initials: Y
authors.lastname: Jeanvoine
mesh_terms: D002413:Cations, Divalent / Q000737:chemistry; D003035:Cobalt / Q000737:chemistry*; D003198:Computer Simulation; D003545:Cysteine / Q000737:chemistry*; D005740:Gases; D008958:Models, Molecular; D008968:Molecular Conformation; D011522:Protons; D012643:Selenium / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D002413:Cations, Divalent; D005740:Gases; D011522:Protons; D003035:Cobalt; D012643:Selenium; D003545:Cysteine