Light harvesting in brown algae

The light harvesting complexes (LHC) of brown algae are embedded in plastid membranes. Besides chlorophyll a, these LHC bind chlorophyll c and fucoxan thin which are efficient for photosynthetic activity. The polypeptides are assembled in vivo into macromolecular complexes with molecular masses rangi ng from 120 to 700 kDa composed of two or several distinct components of 17 -22 kDa. The chlorophyll c-fucoxanthin binding proteins are phylogeneticall y and structurally related to Chla/b-LHC protein. Indeed, the protein conta ins three membrane-spanning helices and possesses the conserved residues id entified in green plants as stabilizing the tertiary structures or binding Chin molecules. However, the localization of Chic and xanthophyll molecules is still unknown. Up to now, it is not clear if in the Chromophyta there a re antennae transmitting the absorbed energy specifically to one or the oth er photosystems. The polypeptides are encoded by a nuclear multigene family but the total number of genes is not yet established in any species. Recen tly, the expression of Lhc genes has been shown to be regulated by light in tensity and under the control of a blue receptor. As perspectives, the reco nstitution of complexes in vitro could help to understand the binding of pi gments to proteins. Cloning and characterization of the chlorophyll c fucox anthin binding protein genes allow molecular biology approaches in the stud ies of the gene expression and also to develop a DNA transformation system for brown algae.