Johannes Heimgärtner


Last Name

Heimgärtner

First Name

Johannes

ORCID

0000-0003-0059-9888

Organisational unit

09740 - Lang, Kathrin / Lang, Kathrin

Filters

2022 - 20253
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Publications 1 - 3 of 3
  • Introducing Azomethine Imines to Chemical Biology: Bioorthogonal Reaction with Isonitriles
    Item type: Journal Article
    Markos, Athanasios; Biedermann, Maurice; Heimgärtner, Johannes; et al. (2023)
    Journal of the American Chemical Society
    Azomethine imines are valuable substrates for chemical synthesis in organic solvents that often require anhydrous conditions. Here, we introduce C,N-cyclic-N'-acyl azomethine imines (AMIs) to bioorthogonal reactions in an aqueous environment. These AMIs are stable under physiological conditions and react rapidly (k2 = 0.1-250 M-1 s-1, depending on pH) and chemoselectively with isonitriles in the presence of biological nucleophiles, including thiols. Live-cell imaging of cell-surface-bound isonitriles underlines the biocompatibility of the AMI-isonitrile ligation, and simultaneous one-pot triple-protein labeling demonstrates its orthogonality to commonly used bioorthogonal reactions, such as the SPAAC and iEDDA ligations.
  • The AMI-isonitrile ligation 2.0: Fast, selective, and pH sensitive
    Item type: Journal Article
    Biedermann, Maurice P.; Markos, Athanasios; Warm, Ian; et al. (2025)
    Chem
    The bioorthogonal ligation between isonitriles and azomethine imines (AMIs)—the AMI-isonitrile ligation—combines exquisite chemoselectivity with a stable ligation product, a small molecular reporter, and a pH-dependent rate. In this work, we tailored the modular structure of the dipolar AMI to increase Brønsted basicity and electrophilicity. These additive structural modifications increased the ligation rate by more than two orders of magnitude to 14 M−1s−1 at pH 7, 140 M−1s−1 at pH 6, and >1,000 M−1s−1 at pH 5. The faster reaction rate at lower pH values allowed for the preferential labeling of live cells at acidic versus neutral pH. This environmental sensitivity paves the way for in vivo targeting of acidic milieus, such as tumors.
  • Site-Specific Protein Labeling and Generation of Defined Ubiquitin-Protein Conjugates Using an Asparaginyl Endopeptidase
    Item type: Journal Article
    Fottner, Maximilian; Heimgärtner, Johannes; Gantz, Maximilian; et al. (2022)
    Journal of the American Chemical Society
    Asparaginyl endopeptidases (AEPs) have recently been widely utilized for peptide and protein modification. Labeling is however restricted to protein termini, severely limiting flexibility and scope in creating diverse conjugates as needed for therapeutic and diagnostic applications. Here, we use genetic code expansion to site-specifically modify target proteins with an isopeptide-linked glycylglycine moiety that serves as an acceptor nucleophile in AEPmediated transpeptidation with various probes containing a tripeptidic recognition motif. Our approach allows simple and flexible labeling of recombinant proteins at any internal site and leaves a minimal, entirely peptidic footprint (NGG) in the conjugation product. We show site-specific labeling of diverse target proteins with various biophysical probes, including dual labeling at an internal site and the N-terminus. Furthermore, we harness AEP-mediated transpeptidation for generation of ubiquitinand ubiquitin-like-modifier conjugates bearing a native isopeptide bond and only one point mutation in the linker region.
Publications 1 - 3 of 3