title: The S-layer Protein DR_2577 Binds Deinoxanthin and under Desiccation Conditions Protects against UV-Radiation in Deinococcus radiodurans.
abstract: Deinococcus radiodurans has the puzzling ability to withstand over a broad range of extreme conditions including high doses of ultraviolet radiation and deep desiccation. This bacterium is surrounded by a surface layer (S-layer) built of a regular repetition of several proteins, assembled to form a paracrystalline structure. Here we report that the deletion of a main constituent of this S-layer, the gene DR_2577, causes a decrease in the UVC resistance, especially in desiccated cells. Moreover, we show that the DR_2577 protein binds the carotenoid deinoxanthin, a strong protective antioxidant specific of this bacterium. A further spectroscopical characterization of the deinoxanthin-DR_2577 complex revealed features which could suggest a protective role of DR_2577. We propose that, especially under desiccation, the S-layer shields the bacterium from incident ultraviolet light and could behave as a first lane of defense against UV radiation.
authors.affiliation: Laboratory of Plant Physiology and Photobiology, Department of Life and Environmental Sciences, University of Cagliari Cagliari, Italy.
authors.forename: Domenica
authors.initials: D
authors.lastname: Farci
authors.affiliation: Department of Physical Chemistry, Institute of Physical and Theoretical Chemistry Frankfurt am Main, Germany.
authors.forename: Chavdar
authors.initials: C
authors.lastname: Slavov
authors.affiliation: Laboratory of Molecular Virology, Department of Life and Environmental Sciences, University of Cagliari Cagliari, Italy.
authors.forename: Enzo
authors.initials: E
authors.lastname: Tramontano
authors.affiliation: Laboratory of Plant Physiology and Photobiology, Department of Life and Environmental Sciences, University of CagliariCagliari, Italy; International Institute of Molecular and Cell BiologyWarsaw, Poland.
authors.forename: Dario
authors.initials: D
authors.lastname: Piano
keywords: DR_2577; Deinococcus radiodurans; S-layer; UV light; deinoxanthin; desiccation; quenching; radiation-resistance