PARENT SESSION
Posters P4Aa Chlorophyll and bilin based antenna systems. Abstracts (239-271)

Giant antenna-PSII super-complex from Acaryochloris marina with binding chlorophyll d. Min Chen^*,1, Thomas Bibby², Jon Nield², Anthony Larkum¹, James Barber², ¹ School of Biological Sciences, University of Sydney, Sydney, NSW, Australia² Department of Biological Sciences, Imperial College London, London, UK

ABSTRACT- Acaryochloris marina is a prochlorophyte-like cyanobacterium containing both phycobilins and chlorophyll d as light harvesting pigments. Using electron microscopy and single particle analyses we show that the chlorophyll d light harvesting system, which is composed of Pcb proteins similar to those that bind chlorophyll a and chlorophyll b in prochlorophytes, functionally associate with the photosystem II (PSII) reaction centre (RC) core to form a giant supercomplex. This supercomplex has a molecular mass of about 2500 kDa and dimensions of 385 X 240 . It is composed of two PSII RC core dimers arranged end-to-end and sixteen flanking Pcb subunits distributed symmetrically along each side. Thus each PSII RC monomer has four Pcb subunits acting as a light harvesting system which increases its absorption cross section of PSII by about 160%. Sequencing analyses and mass spectral protein finger printing indicate that the Pcb proteins associated with PSII are predominates the product of the pcbA gene and more fore remain that question of the role of the other pcb gene (pcbC) in this organism (Chen et al 2004).

KEY WORDS: pcb proteins, chlorophyll d, Antenna-reaction centre supercomplex, Acaryochloris marina