tailieunhanh - Báo cáo Y học: Functional studies of the Synechocystis phycobilisomes organization by high performance liquid chromatography on line with a mass spectrometer

This studywas designed to yield data on the supramolecular organization of the phycobilisome apparatus from Synechocystis, and the possible effects of environmental stress on this arrangement. Phycobilisomes were dissociated ina low ionic strength solutionandaquantitative estimation of the protein components present in each subcomplex was obtained using liquid chromatography coupled on-line with a mass spectrometer equipped with an electrospray ion source (ESI-MS). | Eur. J. Biochem. 269 1534-1542 2002 FEBS 2002 Functional studies of the Synechocystis phycobilisomes organization by high performance liquid chromatography on line with a mass spectrometer Lello Zolla Maria Bianchetti and Sara Rinalducci Dipartimento di Scienze Ambientali Universita degli Studi della Tuscia Viterbo Italy This study was designed to yield data on the supramolecular organization of the phycobilisome apparatus from Synechocystis and the possible effects of environmental stress on this arrangement. Phycobilisomes were dissociated in a low ionic strength solution and a quantitative estimation of the protein components present in each subcomplex was obtained using liquid chromatography coupled on-line with a mass spectrometer equipped with an electrospray ion source ESI-MS . An advantage of this approach is that information can be collected on the initial events which take place as this organism adapts to environmental changes. Ultracentrifugation of whole phycobilisomes revealed five subcomplexes the lightest contained four linker proteins plus free phycocyanin the second the core complex while the last three bands contained the rod complexes. Four linkers were found in band 1 with higher molecular masses than those expected from the DNA sequence indicating that they also contain linked chemical groups. UV-B irradiation specifically destroyed the b-phycocyanin and one rod linker which resulted in the disintegration of the rod complexes. The two bilins present in b-phycocyanin give a greater contribution to the UV absorption than the single bilin of the other bilinproteins and probably react with atmospheric oxygen forming toxic radicals. The protein backbone is in fact protected from damage in anaerobic conditions and in the presence of radical scavengers. Cells grown in sulfur- and nitrogen-defcient medium contained signifcantly reduced levels of b-phycocyanin and one rod linker. Keywords phycobilisomes UV-B irradiation Synechocystis HPLC mass .