Structural basis for the recognition of K48-linked Ub chain by proteasomal receptor Rpn13.Liu, Z., Dong, X., Yi, H.W., Yang, J., Gong, Z., Wang, Y., Liu, K., Zhang, W.P., Tang, C.
(2019) Cell Discov 5: 19-19
- PubMed: 30962947
- DOI: https://doi.org/10.1038/s41421-019-0089-7
- Primary Citation of Related Structures:
- PubMed Abstract:
The interaction between K48-linked ubiquitin (Ub) chain and Rpn13 is important for proteasomal degradation of ubiquitinated substrate proteins. Only the complex structure between the N-terminal domain of Rpn13 (Rpn13 NTD ) and Ub monomer has been characterized, while it remains unclear how Rpn13 specifically recognizes K48-linked Ub chain. Using single-molecule FRET, here we show that K48-linked diubiquitin (K48-diUb) fluctuates among distinct conformational states, and a preexisting compact state is selectively enriched by Rpn13 NTD . The same binding mode is observed for full-length Rpn13 and longer K48-linked Ub chain. Using solution NMR spectroscopy, we have determined the complex structure between Rpn13 NTD and K48-diUb. In this structure, Rpn13 NTD simultaneously interacts with proximal and distal Ub subunits of K48-diUb that remain associated in the complex, thus corroborating smFRET findings. The proximal Ub interacts with Rpn13 NTD similarly as the Ub monomer in the known Rpn13 NTD :Ub structure, while the distal Ub binds to a largely electrostatic surface of Rpn13 NTD . Thus, a charge-reversal mutation in Rpn13 NTD weakens the interaction between Rpn13 and K48-linked Ub chain, causing accumulation of ubiquitinated proteins. Moreover, physical blockage of the access of the distal Ub to Rpn13 NTD with a proximity-attached Ub monomer can disrupt the interaction between Rpn13 and K48-diUb. Taken together, the bivalent interaction of K48-linked Ub chain with Rpn13 provides the structural basis for Rpn13 linkage selectivity, which opens a new window for modulating proteasomal function.
3University of Chinese Academy of Sciences, Beijing, 100049 China.