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"Bacterial light-sensing proteins: how prokaryots ''see'' their world"

Relatore: Wolfgang Gaertner- Max-Planck-Institut for Bioinorganic Chemistry, Muelheim, Germany

Dipartimento di Fisica, aula Maxwell
06 Novembre 2009 ore 14.30

Light was always known as an important regulatory environmental factor. However, detailed information on the molecular mechanisms which initiate photoreceptor function after light absorption could be collected only during recent years. Detailed information will be presented on the light-induced reaction in the red light-sensitive phytochromes and in the blue light-sensitive LOV-domain proteins (LOV, light, oxygen, voltage). Whereas phytochromes act via their covalently bound tetrapyrrole chromophore and undergo a photoisomerization, LOV proteins incorporate their flavin chromophore non-covalently and form a covalent bond to the protein from their triplet state. Of similar importance as the photoreaction is the transmission of the generated biological signal within the photoreceptor and towards “downstream signalling” proteins. Examples will be discussed which show, irrespective of a blue- or a red light-sensing chromophore, the same mechanism of signalling. This signal transduction process, which eventually leads to a physiological response of the organism, is presented for selected, well characterized bacterial systems.