Activity: Fully hydrolyzed by the K48-specific OTUB1* deubiquitylase
Verified Applications: Poly-ubiquitin chains exhibit diversity in length, linkage type, and associated cellular functions. K48-linked tetra-ubiquitin serves as a valuable reagent in assays involving ubiquitin-binding proteins and as a substrate for ubiquitin-specific deubiquitylating enzymes (DUBs). Optimal enzyme concentrations should be empirically determined based on the specific assay context. Note: Exposure of this product to elevated temperatures in SDS-PAGE sample buffer may lead to anomalous high-molecular-weight smearing during electrophoresis, which does not reflect its actual purity. For improved resolution, we recommend pre-incubation in SDS-PAGE buffer at temperatures below 60 °C for 20 minutes prior to gel loading.
2 μg UBA1 run on 4-12% SDS-PAGE gel under reducing conditions, then visualized with Colloidal Coomassie Blue Stain.
Formulation: 10 mM HEPES, pH 7.6
Shipping: The product is shipped with dry ice or equivalent. Upon receipt, store it immediately at the temperature recommended below.
Storage and Stability: Use a manual defrost freezer and avoid repeated freeze-thaw cycles. Aliquot and store ≤ -20°C (stable for 48 months from date of receipt).
Protein Sequence: MQIFVKTLTGKTITLEVEPSDTIENVKAKIQDKEGIPPDQQRLIFAGKQLEDGRTLSDYNIQKESTLHLVLRLRGG
Background Information and Alternate Names
Species & domain architecture
Consists of four ubiquitin units linked via Gly76 → Lys48 isopeptides. The 1.7 Å crystal structure (PDB 2O6V) captures the compact closed conformation, while solution NMR/SAXS ensembles reveal pH-dependent breathing into semi-open states.
UPS pathway role
Lys48-linked tetra-ubiquitin is a high-affinity ligand for the proteasome’s UIM and PRU receptors (Rpn10, Rpn13) and for shuttle adaptors such as hHR23A and Ubiquilin-2. Once attached to a substrate, the tetramer seeds further elongation, recruits p97-Ufd1/Npl4 in ERAD, and allosterically activates the ATPase ring that drives unfolding and translocation.
Relevance to TPD & disease biology
Most PROTACs and molecular glue degraders depend on Lys48 chain formation. Dysregulation of Lys48 chain dynamics underlies neurodegeneration (e.g., defective trimming by ataxin-3) and chemoresistance in cancer. Lys48 enables in vitro evaluation of small-molecule DUB or ligase modulators.
References
Eddins, M. J., et al., (2007) J Mol Biol 367:204-211. PMID 17240395
Grice, G. L., and J. A. Nathan.(2016) Cell Mol Life Sci 73:3497-3506. PMID 27137187
Liu, Z., et al., (2019) Cell Discov. 2:5:19. PMID 30962947
Alternate Names: Human Lys48-linked tetra-ubiquitin (Ub₄-K48, K48-tetraUb)
