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Synthesis and functions of photosynthetic pigments
Chlorophyll is essential for life, directly or indirectly, as the cofactor of photosynthetic proteins that harvest sunlight and convert it to photochemical energy for the cell. The synthesis of chlorophyll is a globally significant pathway resulting in the formation of the most abundant pigment on Earth. Indeed, with hundreds millions of tonnes synthesised every year chlorophyll biosynthesis and degradation are the only biochemical processes that can be observed from outer space.
Top view on photosystem II subunits CP47 (white) and PsbH (blue) with bound chlorophyll (green) and β-carotene (orange) molecules. Function of the CP47 ‘antenna‘ protein is to direct the energy of photons into the reaction center of the photosystem II. Structure of the monomeric photosystem II is shown in the right figure.
Chlorophyll biosynthesis is quite complicated since this molecule is synthetized together with other tetrapyrroles such as heme or vitamin B12 in a long branched pathway. Our work is aimed to elucidate how is the chlorophyll biosynthetic pathway controlled by the photosynthetic cell, what way is this pigment built into photosynthetic complexes and what is the fate of chlorophylls once these complexes are degraded.
Within the lab we use a broad range of approaches including molecular biology and genetics, protein and pigment biochemistry, enzymology or electron microscopy. Our favoured model organism is the cyanobacterium Synechocystis PCC 6803; an excellent genetic ‘tool’ thanks to its efficiency to integrate DNA into its genome via homologous recombination, which allows a simple inactivation/modification of genes of choice.
The upper part of the picture shows cells of the cyanobacterium Synechocystis PCC 6803 as appeared in electron microscopy (van de Meene et al. Arch. Microbiol, 2006). Below is the wild type strain together with two genetically modified mutants exhibiting changed content of photosynthetic pigments.