PARENT SESSION
Posters P1B Photo-oxidative stress, photoinhibition. Abstracts (394-443)

The role of prohibitins in Synechocystis sp. PCC 6803. Marko Boehm^*,1, Myles Barker¹, Remco de Vries¹, Peter Nixon¹, ¹ Department of Biological Sciences, London, United Kingdom

ABSTRACT- A major target of light-induced, irreversible damage in the thylakoid membrane is the photosystem II (PSII) complex, and in particular the D1 reaction centre subunit. In order to maintain PSII activity the cell needs to remove and degrade damaged D1 protein from the reaction centre of PSII and replace it with a newly synthesized copy of D1. The molecular details of the PSII repair cycle are unclear; however recently the FtsH protease (slr0228) was assigned a key role in the degradation of the D1 protein in Synechocystis sp. PCC 6803. In S. cerevisiae it has been found that unassembled proteins of the mitochondrial inner membrane are removed and degraded by proteases homologous to the FtsH protease in Synechocystis sp. PCC 6803, whereas the newly synthesized copies of the protein are protected from degradation by heterooligomeric prohibitin (PHB) complexes. Protein complexes containing the FtsH protease and prohibitin homologues (HflK/C) have been found in E. coli. We have identified five putative prohibitin proteins in Synechocystis sp. PCC 6803 that share the characteristic SPFH domain (stomatins, prohibitins, flotillins and HflK/C). It therefore seems possible that prohibitins may interact with FtsH (slr0228). Several single and multiple deletion mutants have been produced by directed mutagenesis. Pulse-chase experiments and oxygen evolution measurements combined with biochemical methods have been used to test a possible involvement of these proteins in photoinhibition and the PSII repair cycle.

KEY WORDS: prohibitin, photoinhibition, ftsh