Fig. 5: Unique modes of acceptor ubiquitin activation during Lys48-linked poly-ubiquitin chain formation.
From: Mechanism of millisecond Lys48-linked poly-ubiquitin chain formation by cullin-RING ligases
a, Structural superposition of UBE2R2 (cyan) and bound acceptor ubiquitin (UBA; light orange) with the human E2 UBE2K and UBA (PDB 7OJX; gray). Notice dramatic rotation and translation of the acceptor ubiquitins relative to the E2 UBC domains. b, Same as a, except with the yeast E2 Ubc2 (PDB 7MEY). c, Cartoon illustrating distinct molecular solutions for controlling the orientation of UBA by UBE2R2’s synergy loop (top) and the yeast E3 Ubr1’s UB-binding loop (bottom). d, Ribbon diagram of the UBE2R2~UBD–UBA–RBX1 catalytic core (this study) during Lys48-dependent poly-ubiquitin chain formation. e, Same as d, except with the yeast E3 Ubr1 and Ubc2. f, Superposition of UBE2R2 (cyan) and UBA (light orange) with the human E2 UBE2N bound to UBA (gray) during Lys63-linked chain formation (PDB 5AIT). All structural alignments were performed with coordinates from the E2 UBC domains and UBE2R2–UBA from the neddylated CRL2FEM1C chain elongation structure. UBD, donor ubiquitin.
