Simple and efficient knockdown of His-tagged proteins by ternary molecules consisting of a His-tag ligand, a ubiquitin ligase ligand, and a cell-penetrating peptide.

We designed and synthesized hybrid molecules for a protein knockdown method based on the recognition of a His-tag fused to a protein of interest (POI). The synthesized target protein degradation inducers contained three functional moieties: a His-tag ligand (nickel nitrilotriacetic acid [Ni-NTA]), an E3 ligand (bestatin [BS] or MV1), and a carrier peptide (Tat or nonaarginine [R9]). The designed hybrid molecules, BS-Tat-Ni-NTA, MV1-Tat-Ni-NTA, BS-R9-Ni-NTA, and MV1-R9-Ni-NTA, efficiently degraded His-tagged cellular retinoic acid binding protein 2 via the ubiquitin-proteasome system (UPS).

Development of an ON/OFF switchable fluorescent probe targeting His tag fused proteins in living cells.

The fluorescent labeling of target proteins is useful for analyzing their functions and localization in cells, and several fluorescent probes have been developed. However, the fusion of tags such as green fluorescent protein (GFP) to target proteins occasionally affects their functions and/or localization in living cells. Therefore, an imaging method that uses short peptide tags such as hexa-histidine (the His tag) has been attracting increasing attention.

Development of a Small Hybrid Molecule That Mediates Degradation of His-Tag Fused Proteins.

In recent years, the induction of target-protein degradation via the ubiquitin-proteasome system (UPS) mediated by small molecules has attracted attention, and this approach has applications in pharmaceutical development. However, this technique requires a ligand for the target protein that can be incorporated into tailor-made molecules, and there are many proteins for which such ligands have not been found. In this study, we developed a protein-knockdown method that recognizes a His-tag fused to a protein of interest.

A preorganized β-amino acid bearing a guanidinium side chain and its use in cell-penetrating peptides.

A cyclic β-amino acid (APC(Gu)) bearing a side-chain guanidinium group has been developed. The APC(Gu) residue was incorporated into an α/β-peptide based on the Tat(47-57) fragment, leading to an oligomer with substantial helicity in methanol that enters HeLa cells much more readily than does the corresponding Tat α-peptide.