NblB family

NblB has a role in PBS degradation (together with NblA and NblC). A Synechococcus sp. PCC7942 nblB-less mutant was shown to lack the ability to degrade its phycobilisomes during either sulfur or nitrogen limitation and exhibited an increased ratio of phycocyanin to chlorophyll during nutrient-replete growth (Dolganov and Grossman, 1999). NblB is absent from marine picocyanobacteria. Recently Hu et al. (2019) showed that together with NblA, NblB can 1) interfere with chromophorylation as well as chromophore-detachment of phycobiliprotein; 2) promote dissociation of whole phycobilisomes, cores and, in particular, allophycocyanin trimers. 3) While NblA and NblB do not interact with each other, both interact with lyases, apo- and holo-biliproteins; 4) They promote synergistically the lyase-catalyzed chromophorylation of the β-subunit of the major rod component, C-phycocyanin. 5) They modulate lyase-catalyzed and lyase-independent chromophore transfers among biliproteins, with the core protein, ApcF, the rod protein, CpcA, and sensory biliproteins (phytochromes, cyanobacteriochromes) acting as potential traps. Altogether NblA/B can cooperate with the lyases in remodeling the phycobilisomes.