Di-ubiquitin (Ub2, K11-linked) was synthesised enzymatically using wild type ubiquitin, purified by FPLC and K11 only linkage confirmed by mass spectrometry following tryptic digest. Specifically linked di-ubiquitins have utility as substrates for investigating deubiquitinating enzyme (DUB) activity and polyubiquitin chain processing selectivity and in the study of ubiquitin binding and recognition in ubiquitin signalling associated processes.
K11-linked polyubiquitin molecules are thought to be efficient signals for proteasomal degradation and are utilised by the human anaphase-promoting complex (APC/C) and associated DUBs in the regulation of cell cycle progression.
Modification of cellular proteins with polyubiquitin chains occurs in a wide range of signalling pathways and is tightly regulated in order to ensure cellular homeostasis. The function, processing and ultimate fate of polyubiquitinylated proteins is thought to be determined by the nature of the linkage between adjacent ubiquitin molecules in the polyubiquitin chain.
