The generation of catalytically active metalloproteins inside living mammalian cells is a major research challenge at the interface between catalysis and cell biology. Herein we demonstrate that basic domains of bZIP transcription factors, mutated to include two histidine residues at i and i+4 positions, react with palladium(II) sources to generate catalytically active, stapled pallado‐miniproteins. The resulting constrained peptides are efficiently internalized into living mammalian cells, where they perform palladium‐promoted depropargylation reactions without cellular fixation. Control experiments confirm the requirement of the peptide scaffolding and the palladium staple for attaining the intracellular reactivity.
A fragment
of the DNA basic region (br) of the GCN4 bZIP transcription
factor has been modified to include two His residues at designed i and i+4 positions of its N-terminus.
The resulting monomeric peptide (brHis2) does not bind to its consensus target DNA site (5′-GTCAT-3′).
However, addition of Pd(en)Cl2 (en, ethylenediamine) promotes
a high-affinity interaction with exquisite selectivity for this sequence.
The peptide–DNA complex is disassembled by addition of a slight
excess of a palladium chelator, and the interaction can be reversibly
switched multiple times by playing with controlled amounts of either
the metal complex or the chelator. Importantly, while the peptide brHis2 fails to translocate across
cell membranes on its own, addition of the palladium reagent induces
an efficient cell internalization of this peptide. In short, we report
(1) a designed, short peptide that displays highly selective, major
groove DNA binding, (2) a reversible, metal-dependent DNA interaction,
and (3) a metal-promoted cell internalization of this basic peptide.
Bulky ruthenium complexes featuring photolabile thioether ligands selectively metalate sterically accessible guanines in the c-myc GQ after irradiation with visible light. This ruthenation promotes a substancial enhancement in the transcription of this oncogene.
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