Linkage-specific polyubiquitination regulates many cellular processes. The N-terminal fragment of Rabex-5 (Rabex-5 9-73) contains tandem ubiquitin binding domains: A20_ZF and MIU. The A20_ZF-MIU of Rabex-5 is known to bind monoubiquitin but molecular details of polyubiquitin binding affinity and linkage selectivity by Rabex-5 9-73 remain elusive. Here we report that Rabex-5 9-73 binds linear, K63- and K48-linked tetraubiquitin (Ub 4) chains with K d of 0.1-1μM, determined by biolayer interferometry. Mutational analysis of qualitative and quantitative binding data reveals that MIU is more important than A20_ZF in linkage-specific polyubiquitin recognition. MIU prefers binding to linear and K63-linked Ub 4 with sub μM affinities. However, A20_ZF recognizes the three linkage-specific Ub 4 with similar affinities with K d of 3-4μM, unlike ZnF4 of A20. Taken together, our data suggest differential physiological roles of the two ubiquitin binding domains in Rabex-5.
|Number of pages||6|
|Journal||Biochemical and Biophysical Research Communications|
|Publication status||Published - 2012 Jul 13|
Bibliographical noteFunding Information:
We thank Prof. Hongtae Kim for assistance in pull-down assays. This work was supported by the Korea Science and Engineering Foundation (KOSEF) grant funded by the Korea government (MEST) (2008-0058783) and the Agency for Defense Development through Chemical and Biological Defense Research Center to S.L., and the National Junior Research Fellowship (NRF-2011-0031264) to D.S. from the National Research Foundation (NRF) grant funded by the Ministry of Education, Science, and Technology (MEST) of Korea.
All Science Journal Classification (ASJC) codes
- Molecular Biology
- Cell Biology