For production of poly-ubiquitin chains via K33 only. Recombinant untagged protein
K33-only ubiquitin contains only a single lysine at position 33, with all other lysines mutated to arginine. This mutation renders ubiquitin able to form multi-ubiquitin chains only via K33, while preserving the ability to form an active thioester at the C-terminus and, therefore, the ability of K33-only ubiquitin to be transferred to the lysines of substrate proteins.
