Chemistry Labs

Biochemistry and biomedical chemistry

PROTACs, targeted protein degradation

PROTACs are heterobifunctional molecules that redirect cellular protein-quality-control machinery to degrade a selected target.

1 Lower secondary2 Upper secondary3 Undergraduate4 Advanced5 Research

IntuitionIntuition: the central idea

PROTACs are heterobifunctional molecules that redirect cellular protein-quality-control machinery to degrade a selected target.

Explore the schematic model; it illustrates a concept rather than replacing experimental evidence.

SchoolSchool level: key concepts and a first application

Definition: Core concept

One end binds a protein of interest and the other an E3 ubiquitin ligase. Productive ternary-complex formation can trigger ubiquitination and proteasomal degradation; the degrader may act catalytically.

A PROTAC usually has a target ligand, linker and E3-recruiting ligand. Linker length, exit-vector orientation and ternary-complex cooperativity are central design variables.

Key terms and meaning
TermInterpretation
POIProtein of interest selected for degradation.
E3 ligaseEnzyme recruiting ubiquitin-transfer machinery to substrates.
Hook effectReduced efficacy at excess degrader when binary complexes dominate.

Example: Apply the idea

Why may increasing PROTAC concentration eventually reduce degradation in some systems?

Solution

At high concentration, separate binary target–PROTAC and E3–PROTAC complexes can dominate over productive ternary complexes, producing a hook effect.

UndergraduateUniversity level: quantitative description

Target+PROTAC+E3⇌ternary complex→ubiquitination\text{Target}+\text{PROTAC}+\text{E3}\rightleftharpoons\text{ternary complex}\rightarrow\text{ubiquitination}

A useful degrader must form a ternary complex, catalyse ubiquitination efficiently enough for turnover, and avoid hook-effect losses at elevated concentration.

AdvancedAdvanced: assumptions and mechanistic detail

The mechanism is event-driven rather than occupancy-driven: one degrader molecule can mediate multiple turnover cycles. Molecular glues, molecular degraders and PROTACs form a related design family.

ResearchResearch frontier: open questions and current practice

References