Regulated Proteolysis of the Phycobilisome

Cyanobacteria, much like other photosynthetic organisms, adjust their light harvesting apparatus in response to environmental cues. This tuning allows effective light absorbance for the phototrophic metabolism while preventing the deleterious effect of surplus excitation. The phycobilisome, the cyanobacterial pigment antenna, is a supramolecular assembly that may reach 4 MDa. A small protein, NblA, is essential for the degradation of this pigment complex under nutrient limitation. We recently revealed that this small protein associates with phycobilisomes attached to the photosynthetic membranes. We propose that NblA serves a dual function: undermining complex stability and designating the dissociated pigments for degradation (see “Our Projects” for details).