PROTACs or Proteolysis Targeting Chimeric Molecules are heterobifunctional nanomolecules that theoretically target any protein for ubiquitination and degradation. In terms of the structure, PROTACs consist of one moiety which is recognized by the E3 ligase. This moiety is then chemically and covalently linked to a small molecule or a protein that recognizes the target protein. The trimeric complex formation leads to the transfer of ubiquitins to the target protein.
https://www.medchemexpress.com/Pathways/PROTAC.html