Learte Aymamí, SorayaVidal Vives, ChristianGutiérrez González, AlejandroMascareñas Cid, José Luis2020-06-022021-03-112020S. Learte-Aymamí, C. Vidal, A. Gutiérrez-González, J. L. Mascareñas, Angew. Chem. Int. Ed. 2020 , 59 , 91491433-7851http://hdl.handle.net/10347/22787The 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 reactivityeng© 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versionsjournal article10.1002/anie.2020020321521-3773open access