Fig. 5.

Conserved interactions stabilise the position of ubiquitin in RING-Ubc13~Ub complexes. a The distal (D) RING and bound E2~Ub conjugate from TRIM25-Ubc13~Ub (PDB: 5EYA) and RNF4-Ubc13~Ub (PDB: 5AIU) were overlaid onto TRAF6-Ubc13~Ub. Zinc atoms are shown as purple spheres. (D) refers to the distal RING, (P) proximal. The RING domains are indicated with red outlines. b A detailed view of the contacts between the distal RING and ubiquitin that stabilise the closed conformation. Predicted hydrogen bonds are indicated by dashed lines, and sticks are coloured by atom type (oxygen, nitrogen and sulphur atoms are coloured red, blue and yellow, respectively. Carbon atoms are coloured the same as ribbon). c An overlay of four RING domains (PDBs: TRIM5α 4TKP; TRIM32 5FEY; LNX2 5DIN; RNF125 5DKA) on the RING from DrRZ₃ highlighting the conserved position of the C-terminal alpha helix. On the right is a detailed view of the putative ubiquitin-gripping residues from these RING domain structures. RNF125 is modelled as a dimer, though it is monomeric in PDB 5DKA