Branching via K11 and K48 Bestows Ubiquitin Chains with a Unique Interdomain Interface and Enhanced Affinity for Proteasomal Subunit Rpn1 (Structure)

Boughton et al. characterize branched K11/K48-linked tri-ubiquitin structurally (X-ray crystallography, NMR, SANS) and biochemically and show that it possesses a unique, previously unobserved hydrophobic interface between the distal ubiquitins. This branching enhances binding affinity for proteasomal receptor Rpn1, allowing branched K11/K48-linked polyubiquitins to act as high-priority signals for proteasomal degradation.