a, Side and top views of the EXP2 heptamer in the engaged state. Symmetric portions that remain constant between protomers are coloured in mint. Portions that vary between protomers are coloured and labelled by protomer. b, c, Superposition of the seven EXP2 protomers, labelled A–G, in the engaged (b) and resetting (c) states, coloured as in a. d, e, Top view of HSP101 NBD1 (d) and NBD2 (e) in the engaged and resetting states, shown in simplified surface representation. The hinge point at the interface between HSP101 protomers 3 and 4 is indicated. f, g, Ribbon diagrams of the resetting state (f) and engaged state (g) nucleotide binding pockets are shown for each protomer. ATPγS in each pocket is shown with corresponding cryo-EM density (mesh). The R859 arginine finger (sidechain shown in red-orange) is positioned approximately 3–5.5 Å from the phosphorus atom in the γ-phosphate of the ATPγS in the binding pocket of the neighbouring protomer in all protomers except R859 in protomer 3 in the resetting state (sidechain shown in gold), where the ATPγS bound in the protomer 4 NBD2 nucleotide pocket has shifted approximately 7.5 Å away from the protomer 3 R859 arginine finger. h, i, Enlarged side view of the atomic models of the HSP101 NBD2 pore loops and unfolded cargo polypeptide backbone in the engaged (h) and resetting (i) states, shown with corresponding cryo-EM densities. Tyrosine sidechain densities are clearly visibly intercalating with the cargo densities. The modelled PTEX cargo has a calculated r.m.s.d. of 1.09 Å and 1.25 Å to the published YME1 and HSP104 cargo models, respectively. Pore loops are labelled by NBD and protomer (for example, D2PL,P1 is NBD2 pore loop, protomer 1).