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.


 

References:

Nichols, R.J., B. LaFrance, N.R. Phillips, D.R. Radford, L.M. Oltrogge, L.E. Valentin-Alvarado, A.J. Bischoff, E. Nogales, and D.F. Savage. (2021). Discovery and characterization of a novel family of prokaryotic nanocompartments involved in sulfur metabolism. Elife 10:.
Triccas, J.A., P.W. Roche, N. Winter, C.G. Feng, C.R. Butlin, and W.J. Britton. (1996). A 35-kilodalton protein is a major target of the human immune response to Mycobacterium leprae. Infect. Immun. 64: 5171-5177.
Examples:

TC#NameOrganismal TypeExample
1.S.8.1.1

Type 2A encapsulin shell protein SrpI (SynE7) of 306 aas.  See fanily description for details (Nichols et al. 2021).

SrpI of Synechococcus elongatus PCC 7942

 
1.S.8.1.2

Encapsulin of 307 aas, a type 2A encapsulin shell protein, EncP2 It forms encapsulin nanocompartments about 24 nm in diameter from 60 monomers. Probably encapsulates at least cysteine desulfurase (CyD, AC O32975) and allows passage of cysteine into its interior, probably involved in sulfur metabolism (Triccas et al. 1996).

EncP2 of Mycobacterium leprae

 
1.S.8.1.3

Type 2A encapsulin shell protein of 303 aas. The protein has two halves, the N-terminal domain is uniformly hydrophilic while the C-terminal domain contains 4 short regions of moderate hydrophobicity. 

 

Encapsulin of Hyphomicrobium nitrativoran