Shell component of a type 2A encapsulin nanocompartment. Forms encapsulin nanocompartments about 24 nm in diameter from 60 monomers, probably involved in sulfur metabolism (By similarity). Probably encapsulates cysteine desulfurase (Probable). The encapsulin nanocompartment is formed by 60 subunits; monomers form pentamers which assemble to form shells. There are 12 charged pores where the pentamers meet as well as 3-fold axis channels and dimer channels (By similarity). Isolated from bacteria in a complex with cysteine desulfurase (AC Q9KII6) (PubMed:25500374). Has 4 domains; an N-terminal arm not found in the type 1 subfamily, a discontinuous peripheral domain (P), an elongated loop (E) and the discontinuous axial domain (A). Detected in antisera from mice immunized with killed bacteria but not live bacteria (PubMed:11549181). Cattle naturally infected with M.paratuberculosis all have antisera that recognize this protein (PubMed:25500374). Belongs to the encapsulin family. Family 2A subfamily.