Fig. 6: Architecture of double-loaded SUMO E1 and comparison to other Ubls.
From: Cryo-EM structures reveal the molecular mechanism of SUMO E1–E2 thioester transfer
a, Left, schematic of a trapped SUMO E1–UBC9–SUMO1(t)/SUMO1(a) complex. Middle, cryo-EM map of double-loaded SUMO E1–UBC9–SUMO1(t)/SUMO1(a) complex. Right, cartoon representation of the double-loaded SUMO E1–UBC9–SUMO1(t)/SUMO1(a) complex model. Inset, relative distances among UBA2 C173, UBC9 C93 and SUMO1(t) G97 within the active sites. b, Double-loaded SUMO E1–UBC9–SUMO1(t)/SUMO1(a) complex shown as a surface representation. E1 and E2 are colored gray and black, respectively. SUMO1(a) and SUMO1(t) are colored shades of yellow. c, E2-free double-loaded UBA1 (PDB 4NNJ; left), double-loaded UBA1–CDC34 model with Ub(t) in the open conformation (PDB 7K5J; middle) and double-loaded UBA1–CDC34 model with Ub(t) in the closed conformation (PDB 7K5J; right) are shown as surface representations. E1 and E2 are colored gray and black, respectively. Ub(a) is colored cyan, Ub(t)OPEN is colored aqua blue and Ub(t)CLOSED is colored dark blue. The double-loaded models were created by docking Ub(a) onto the Ub(a) binding site of UBA1 in the states preceding thioester transfer (UBA1–CDC34–Ub(t)OPEN) and following thioester transfer (UBA1–CDC34–Ub(t)CLOSED). d, Double-loaded NEDD8 E1–NEDD8(t)/UBC12/NEDD8(a) is shown as a surface representation in two views rotated 90° about the x axis. E1 and E2 are colored gray and black, respectively. NEDD8(a) and NEDD8(t) are colored shades of green. Right, catalytic cysteines of NEDD8 E1 and UBC12 are colored hot pink and the ~23-Å distance between them is highlighted. e, Double-loaded UBA7–UBE2L6–ISG15(t)/ISG15(a) complex shown as a surface representation in two views rotated 90° about the x axis. E1 and E2 are colored gray and black, respectively. ISG15(a) and ISG15(t) are colored shades of pink.
