Linkage-specific polyubiquitin chains may be used as a substrate for in vitro reactions with deubiquitinating enzymes ("DUB's") that cleave the peptide of isopeptide linkage between adjacent ubiquitin molecules. Polyubiquitin chains can also be used to investigate mechanisms of binding and recognition between the chains and other proteins that contain Ubiquitin-Associated domains (UBA's), Ubiquitin-Interacting Motifs (UIM's), ZnF's, and/or other ubiquitin-sensing elements.
K11/K48-branched polyubiquitin chains facilitate rapid substrate delivery to the proteasome, which prevents accumulation of aggregation-prone nascent proteins. Furthermore, enzymes and effectors of K11/K48-linked chains are encoded by essential genes that are often mutated in neurodegenerative diseases, providing proof that heterotypic ubiquitin chains play important roles in cellular signaling pathways.
The correctness of linkage and purity of each production lot of this product is assessed using the Absolute Quantitation of Ubiquitin Method (Ub-AQUA), an LCMS-based technique that provides extremely accurate information of the composition of polyubiquitin samples. The product is also tested in a Western Blot application described by Yau et al.
