Assembly and structure of Lys33-linked polyubiquitin reveals distinct conformations

Ubiquitylation regulates a multitude of biological processes and this versatility stems from the ability of ubiquitin to form topologically different polymers of eight different linkage types. While some linkages have been studied in detail, other linkage types including Lys33-linked polyubiquitin are poorly understood. Here we identify an enzymatic system for the large-scale assembly of Lys33 chains by combining the HECT (homologous to the E6-AP carboxyl terminus) E3 ligase AREL1 (apoptosis-resistant E3 ubiquitin protein ligase 1) with linkage selective deubiquitinases (DUBs). Moreover, this first characterisation of the chain selectivity of AREL1 indicates its preference for assembling Lys33- and Lys11-linked ubiquitin chains. Intriguingly, the crystal structure of Lys33-linked diubiquitin (diUb) reveals that it adopts a compact conformation very similar to that observed for Lys11-linked diUb. In contrast, crystallographic analysis of Lys33-linked triUb reveals a more extended conformation. These two distinct conformational states of Lys33-linked polyUb may be selectively recognized by ubiquitin binding domains and enzymes of the ubiquitin system. Importantly, our work provides a method to assemble Lys33–linked polyubiquitin that will allow further characterization of this atypical chain type.

Source: BJ Signal - February 27, 2015 Category: Biochemistry Authors: Y Adi Kristariyanto, S Choi, S Abdul Rehman, M Ritorto, D G Campbell, N A Morrice, R Toth, Y Kulathu Tags: BJ Signal Source Type: research