E3 Ligase Recruiters for PROTAC Design

E3 Recruiter Ligandalyzer is designed as a structure-first, ligand-centric platform for recruiter selection before degrader assembly. Instead of treating the recruiter as a single static fragment, it helps users compare recruiter chemotypes, binding poses, solvent exposure, scaffold families, and export readiness.

The explorer view helps users compare recruiter ligands in chemical-property space before committing to one ligase family or chemotype. That is useful because the right recruiter is rarely determined by a single metric.

• Compare MW, LogP, QED, scaffold class, and recruiter class across ligases.
• Look for crowded familiar clusters and underexplored regions that may still be tractable.
• Use ligand-level inspection to move from global chemical space into a specific recruiter hypothesis.
• Remember that a compact recruiter with attractive descriptors can still fail if its geometry or exposure is wrong.

Recruiter-level pages combine 2D chemistry with 3D protein-ligand context so users can check whether a proposed exit vector is actually accessible in the bound pose.

• Prefer solvent-exposed atoms when considering recruiter-side linker attachment.
• Avoid modifying atoms that drive key binding interactions unless SAR or structural evidence supports the change.
• Compare SASA-style exposure metrics with the surrounding pocket geometry rather than trusting one numeric feature alone.
• Use the structure view to decide whether the apparent 2D exit vector is blocked, buried, or sterically awkward in 3D.

Some E3 ligases have many recruiter structures and many scaffold families, while others remain sparse. That does not automatically make the most populated ligase the best biological choice, but it does change how much design information you can work with.

• More structures usually mean more confidence in pose comparison and attachment-site reasoning.
• More scaffold diversity means more chemotype options when one recruiter class adds too much burden or exposes the wrong vector.
• Lower-coverage ligases may still be attractive if the biology or expression context is compelling.
• E3 choice should combine structural coverage, recruiter chemistry, expression context, target biology, and downstream modeling.

The aligned structure viewer helps users compare multiple recruiter-bound complexes for a single ligase, which is where geometry-aware recruiter selection becomes especially useful.

• Compare binding orientations, conserved interactions, and ligand placement within the same pocket.
• Toggle ligands, proteins, pocket views, and interaction overlays to understand steric constraints.
• Use these overlays to compare how different recruiters expose different vectors even when they bind the same ligase.

Scaffold analysis helps users reason about recruiter families instead of single analogues. That is useful when a familiar recruiter binds well but carries the wrong properties, exposure pattern, or synthetic burden for a downstream degrader program.

• Bemis-Murcko-style scaffold organization highlights recurring recruiter cores.
• Frequency and network connectivity can reveal well-reused chemotypes versus ligase-specific chemotypes.
• Scaffold diversity supports recruiter repurposing, analogue selection, and underexplored-chemotype prioritization.

E3 Ligandalyzer is intentionally upstream of PROTAC Builder. Once a recruiter is selected, users can choose an attachment atom and export the recruiter into PROTAC Builder as an editable 2D structure for linker attachment and degrader assembly.

• Preserve continuity between recruiter inspection, exit-vector selection, and linker design.
• Carry the selected attachment point forward instead of re-deciding it after assembly has already started.
• Use PROTAC Builder to pair the recruiter with warheads, enumerate candidate linkers, and prepare downstream handoffs.