Fig. 3: Cryo-EM single particle structure of the encapsulin shell of M. tuberculosis.
From: In situ and in vitro cryo-EM reveal structures of mycobacterial encapsulin assembly intermediates
a Electron-density map of the encapsulin shell. Each of the twelve pentamers consists of five Enc monomers (coloured orange, black, teal, yellow and purple in the central pentamer). The centre of each pentamer contains the fivefold symmetry pore (black arrow). Pores are also present at the points of threefold symmetry (white arrow) and on the interface between two Enc subunits (red arrow). Scalebar: 25 Å. b Atomic model ribbon view of the encapsulin shell of M. tuberculosis. scalebar: 25 Å. c Selection of the atomic model ribbon view in panel B to indicate the centre of the trimer (black pentamer), trimer (green triangle) and dimer (red double headed arrow). A total of 30 dimers, 20 trimers and 12 pentamers are present in the T = 1 encapsulin shell, where each Enc subunit is part of one dimer, trimer and pentamer. Scalebar: 25 Å. d Ribbon view of the Enctb monomer with domains shown in different colours: P-domain (purple), A-domain (orange), E- loop (teal) and F-loop (green). Scalebar: 10 Å. e–g Ribbon view of the dimer, trimer and pentamer respectively with the domains shown in the same colour as panel D. Scalebar: 25 Å. h Overlay of the Enc monomers of M. tuberculosis (purple, this study, EMD-13164), M. hassiacum (teal, RCSB accession number 6I9G8), T. Maritima (orange, RCSB accession number 7K5W5) and Q. thermotolerans (yellow, (EMDB accession number 938311). Scalebar: 10 Å. i–k Coulomb surface of the pores present on the interface between two subunits (yellow arrows) and on the points of three- and fivefold symmetry respectively. A point of twofold symmetry, where no clear pore is present, is indicated with a cyan arrow in panel (i). Positive charge is displayed in blue (10 kcal/(mol·e)) and negative charge in red (−10 kcal/(mol·e)). Scalebars: 10 Å.
