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Updated: May 24, 2026

Assaying Proteasomal Degradation in a Cell-free System in Plants
Published on: March 26, 2014
Polyubiquitin recognition by AtSAP5, an A20-type zinc finger containing protein from Arabidopsis thaliana
Hoon Choi1, Seungsoo Han, Donghyuk Shin
1Department of Biological Sciences, Sungkyunkwan University, Suwon 440-746, Republic of Korea.
Abstract:
Stress associated proteins (SAPs) in plants contain A20-type zinc finger (A20_ZF) domains and are involved with abiotic stress response. A20-type zinc finger domains in animals reportedly recognize ubiquitin as a regulatory signal in cell. However, it remains unclear whether A20_ZF domains in plants perform similar roles. AtSAP5, a SAP from Arabidopsis thaliana, exhibits a unique sequence feature among 10 AtSAPs harboring A20_ZF domains. The highly conserved diaromatic patch is replaced by the dialipathic patch. Here we investigated whether AtSAP5 recognizes ubiquitin and the roles of the dialipathic patch in ubiquitin binding in vitro. GST pulldown assay reveals that AtSAP5 binds polyubiquitin rather than monoubiquitin. AtSAP5 shows preferences for linear and K63-linked polyubiquitin chains to K48-linked one. The A20_ZF domain of AtSAP5 is sufficient for linkage-specific polyubiquitin recognition. The dialipathic patch in AtSAP5 plays an important role in K48-linked polyubiquitin recognition. Taken together, our results suggest that AtSAP5 participates in polyubiquitin recognition in plants and that the dialipathic patch in AtSAP5 is critical in binding K48-linked polyubiquitn chains.
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