Figure 2.

Typical and atypical ubiquitin chains: ubiquitin can be attached to proteins as a single unit on one or multiple sites, yielding monoubiquitinated and multimonoubiquitinated proteins, respectively. Ubiquitin contains 7 Lys residues (Lys⁶, Lys¹¹, Lys²⁷, Lys²⁹, Lys³³, Lys⁴⁸, or Lys⁶³) that can serve as acceptor sites for additional ubiquitin molecules generating poly-ubiquitinated proteins with distinct types of ubiquitin conjugation. The scheme shows the most representative ubiquitin chains.