ASSEMBLY OF THE CHLOROPHYLL-PROTEIN COMPLEXES

The biogenesis of photosynthetic complexes in plants and algae is a mu lti-step process that involves intricate coordination of steps in two intracellular compartments, the chloroplast and the cytoplasm. The pro cess initiates with the transcription and translation of the various p olypeptide subunits. The nuclear-encoded Chl-binding proteins are tran slated on cytoplasmic ribosomes as precursors that have a transit (lea der) sequence at their amino-terminus. The precursors are post-transla tionally imported into the chloroplasts, proteolytically processed int o their mature forms, inserted into the thylakoid membrane, and bound to their co-factors (and pigments) and with other subunits to form an active complex. The order and mechanisms by which these events occur, are currently being discovered. Electrostatic interactions, the 'posit ive inside rule', interhelix interactions, interactions with lipids an d chaperone proteins affect the insertion and stabilization of the Chl -proteins in the thylakoids. This review describes the events occurrin g during the integration and organization of the Chl-proteins.