Fig. 1.

Overview of encapsulin nanocompartment structure and assembly. (A) An encapsulin shell monomer from the Thermotoga maritima encapsulin system in ribbon representation (purple; PDB: 3DKT). Left: exterior view. Right: interior view (180° rotated). The interior binding site of the Family 1 encapsulin targeting peptide outlined in light blue. (B) Exterior views of the T=1 encapsulin from T. maritima (left; PDB: 3DKT), the T=3 encapsulin from Myxococcus xanthus (center; PDB: 4PT2), and the T=4 encapsulin from Quasibacillus thermotolerans (right; PDB: 6NJ8) highlighting the different sizes and assembly states of encapsulins. The number of pentameric and hexameric facets that make up the shell are shown at the bottom. (C) Schematic of the Q. thermotolerans encapsulin with a T=4 icosahedral cage overlay highlighting the respective five-fold (left), three-fold (center), and two-fold (right) symmetry axes and pores, with respective magnified views below. (D) Schematic diagram of Family 1 and Family 2 core operon layouts (top) featuring the cargo (pink), respective targeting moieties (turquoise), and encapsulin shell (purple); note Family 1 and 2 cargo genes are found up- and downstream of the encapsulin gene, respectively. For simplicity, only the upstream operon organization is shown. Figures created using ChimeraX (Goddard et al., 2018). PDB, protein data bank; TD, Family 2 targeting domain; TP, Family 1 targeting peptide.