Shell component of a type 1 encapsulin nanocompartment. Assembles into proteinaceous icosahedral shells 24 nm in diameter in the presence and absence of its ferritin cargo protein. The center of cargo-loaded nanocompartments is loaded with iron. The empty encapsulin nanocompartment sequesters about 2200 Fe ions while the cargo-loaded nanocompartment can maximally sequester about 4150 Fe ions. Does not have any detectable ferroxidase activity. This encapsulin nanocompartment is formed by 60 subunits; monomers form pentamers which assemble to form shells. There are 12 pores where the pentamers meet as well as 3-fold axis channels and dimer channels; none are larger than 3-4 Angstroms in diameter. The N-terminus of the protein is inside the shell, the C-terminus is outside. Belongs to the encapsulin family. Family 1 subfamily.