PARENT SESSION
Posters P8B Supermolecular organization of the photosynthetic apparatus. Abstracts (592-611)

Isolation and structural analysis of photosynthetic antenna complexes in the cyanobacterium Fischerella muscicola PCC 73103. James Duncan^*,1, James Barber¹, ¹ Faculty of Life Sciences, London, UK

ABSTRACT- Fischerella muscicola PCC 73103 is a little studied heterocystous filamentous cyanobacteria, originally discovered in a rice field. It has been shown by Geiss et al, that Fischerella muscicola has an iron stress induced isiA gene. However, in contrast to unicellular non filamentous cyanobacteria, where the isiB gene encoding flavodoxin is located downstream of isiA gene, Fischerella muscicolahas a gene similar to the pcb light harvesting gene found in prochlorophytes, which is expressed on the same iron stress induced operon, downstream of the isiA gene. Thylakoid membranes from Fischerella muscicola were isolated from cells grown in the presence and absence of iron and reaction centre complexes were isolated by mild solubilisation with dodecyl maltoside and sucrose density gradient purification. As no structural work had been carried out on Fischerella muscicola prior to this study, negative stain electron microscopy and single particle analysis was used to investigate the oligomeric states of the photosynthetic reaction centre complexes in Fischerella muscicola when grown in the presence of iron. Furthermore, a unique Pcb-PSI light harvesting antenna complex was isolated and structurally characterised, using single particle analysis, from cells grown under iron deficient conditions, where 8 Pcb subunits can associate with monomeric photosystem I reaction centre of Fischerella muscicola.

KEY WORDS: antenna, PSI, electron microscopy, Pcb