Photochemie und Signaltransduktion von Blaulichtrezeptorproteinen aus photosynthetisierenden Mikroorganismen
The light activated kinase Phototropin from Chlamydomonas reinhardtii, the photoactivated adenylylcyclase (PAC) from Euglena gracilis and the BLUF protein Slr1694 from Synechocystis sp. PCC 6803 were investigated concerning the molecular details of the primary photochemistry as well as signal transduction. Phototropin was isolated from Escherichia coli in mg amounts after solubilization with arginine. Without arginine E. coli cAMP receptor protein, which shows high homology to a cAMP activated kinase from C. reinhardtii, was copurified. Full length Phototropin shows similar photochemistry to LOV-domain containing proteins without the kinase including triplet and covalent cysteinyl adduct formation. Signaling state decay is accelerated in the presence of ATP and suggests photoreceptor-kinase interaction. FTIR spectroscopy showed light induced structural changes in the kinase domain. The distance of the photoreceptor domains of 25 Angstrom was determined by ELDOR spectroscopy. Mutation of the side chains of S28, N31 and W91 in Slr1694 showed no conserved influence on the dynamic of the signaling state. Removal of the hydroxyl group of S28 lead to a 15 nm red shift of the absorption spectrum as a result of altered hydrogen bond coordination of the cofactor. Introduction of positively charged side chains at the position of N31 strengthened the binding of phosphorylated flavins. An artificial flavin like roseoflavin was introduced in Slr1694 by coexpression of a bacterial flavin transporter. The essential role of M152 in PAC for signal transduction was shown by determination of light activated cAMP synthesis activity. Ultrafast IR spectroscopy confirmed the contribution of Y8 and Q50 in the photocycle and gave a more detailed description of the hydrogen bonding situation in the signaling state.
School:Humboldt-Universität zu Berlin
Source Type:Master's Thesis
Keywords:WD 2800 Phototropin Photoactivierte Adenylatcyclase Blaulichtrezeptor Heterologe Expression Chlamydomonas reinhardtii Synechocystis Euglena gracilis photoactivated adenylyl cyclase blue light receptor transient spectroscopy heterologous expression
Date of Publication:01/03/2008