This dance represents a novel bivalent MDM2 assay which investigates protein allostery utilizing functionalized nanoparticles and surface-enhanced Raman spectroscopy (SERS).

The tumour suppressor protein, p53, is either mutated or absent in over 50% of cancers. MDM2 is a negative regulator of p53 found to be upregulated in some of these cases. p53-MDM2 interactions are therefore prime targets for novel chemotherapeutic development. MDM2 putatively dimerizes via the C-terminal RING domain and the N-terminal hydrophobic pocket is involved in an initial binding event to the BOX-1 domain of p53. This causes a conformational change in MDM2 that allows for further interactions with p53 and subsequent negative regulation.

The Dance
Nanoparticles (yellow t-shirts) are functionalized with a dye-labeled p53 peptide mimic (red wristbands) which represents the p53 BOX-1 domain. MDM2 (white t-shirts) dimerizes via the C-terminal domain and binds the p53 peptide mimic on the nanoparticle surface through the N-terminal domain. This initiates nanoparticle assembly which results in an increased SERS intensity (rhythmic raised arm movements and lighting changes).

Introduction of an MDM2 N-terminal ligand (spotty sock) to the solution blocks the binding site on the protein. Nanoparticles can only bind where no ligand is present therefore assembly is inhibited and no SERS increase is observed.

MDM2 RING domain peptides (stripy socks) bind the RING domain mimicking the dimerization interaction and preventing protein dimer formation. MDM2 molecules are able to bind functionalized nanoparticles via the N-terminal domain however assembly is not possible and no increase in SERS intensity is observed.

The assay described demonstrates potential for screening MDM2-p53 ligand inhibitors. Molecules that inhibit the assembly process could then potentially be used in the development of novel chemotherapeutics. Socks represent these theoretical inhibitor molecules attacking cancer (red man).

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