Fig. 1: Overall architecture of a SUMO E1–UBC9/SUMO1(a) complex.
From: Cryo-EM structures reveal the molecular mechanism of SUMO E1–E2 thioester transfer
a, Schematic of the SUMO E1–E2 thioester transfer reaction. The ‘inactive’ state is shown, where the catalytic cysteines of SUMO E1 and UBC9 are distal. Upon conformational change, both the catalytic cysteines come in proximity and form a tetrahedral intermediate with SUMO1(a). SUMO E1 in complex with adenylated SUMO1(a) is termed as ‘singly loaded’. b, Schematic (left) and purification (right) of a trapped SUMO E1–UBC9/SUMO1(a) complex. c, Left, cryo-EM map of SUMO E1–UBC9/SUMO1(a) complex colored and labeled as indicated. Right, cartoon representation of the model. The catalytic cysteines of SUMO E1 and UBC9 are shown as yellow spheres. Adenosine monophosphate (AMP) and zinc are shown as spheres and colored in lime and gray, respectively. d, Domain organization of heterodimeric SUMO E1 (UBA2 and SAE1) with domains colored as in c. e, SUMO E1 atoms contacting UBC9 colored by domain, as in c. Aden., adenylation; Conf., conformational; PURE, purified; DTT, dithiothreitol.
