1.S.8.  The Bacterial/Archaeal Nanocompartment Encapsulin Shell Protein3 (BANC-SP3) Family 

Prokaryotic nanocompartments, encapsulins, are a proteinaceous organelle-like compartment in prokaryotes that compartmentalize cargo enzymes. While initial studies have begun to elucidate the structures and physiological roles of encapsulins, bioinformatic evidence suggests that a great diversity of encapsulin nanocompartments remains unexplored. Nichols et al. 2021 described a novel encapsulin in the freshwater cyanobacterium Synechococcus elongatus PCC 7942. This nanocompartment is upregulated upon sulfate starvation and encapsulates a cysteine desulfurase enzyme via an N-terminal targeting sequence. Using cryo-electron microscopy, the structure of the nanocompartment complex to 2.2 Å resolution was determined. Bochemical characterization of the complex demonstrated that the activity of the cysteine desulfurase is enhanced upon encapsulation.