caratterizzazione funzionale di un canale del potassio del cianobatterio Synechocystis sp. PCC 6803

My Ph.D. project was focused on the characterization of a prokaryotic potassium channel, called SynK, that was identified in the genome of the cyanobacterium Synechocystis sp. PCC6803, a photoheterotrophic organism. SynK was cloned, expressed, and assigned as a potassium selective channel. In order to study its physiological role, I produced a SynK-deficient Synechocystis strain, which is unable to grow under normal illumination conditions. Growth may be restored if an electron donor is added or if high-intensity illumination is applied. Western blotting experiments, performed with antibodies raised against SynK, revealed that expression of the channel protein is correlated with growth and seems to be regulated by redox-state. The location of SynK in thylakoid membranes was shown by immunogold electron microscopy. Fluorimetric experiments indicated that SynK-deficient cyanobacteria are unable to build up a proton gradient across the thylakoid membrane upon illumination. These data indicate the crucial role played by SynK in regulating photosynthesis in these organisms. I also worked on purification and molecular characterization of a higher plants thylakoid potassium channel that was identified by immunoblot using antibodies raised against the prokaryotic channel.