Trimethyllysine is an important post-translationally modified amino acid with functions in the carnitine biosynthesis and regulation of key epigenetic processes. Protein lysine methyltransferases and demethylases dynamically control protein lysine methylation, with each state of methylation changing the biophysical properties of lysine and the subsequent effect on protein function, in particular histone proteins and their central role in epigenetics. Epigenetic reader domain proteins can distinguish between different lysine methylation states and initiate downstream cellular processes upon recognition. Dysregulation of protein methylation is linked to various diseases, including cancer, inflammation, and genetic disorders. In this review, we cover biomolecular studies on the role of trimethyllysine in carnitine biosynthesis, different enzymatic reactions involved in the synthesis and removal of trimethyllysine, trimethyllysine recognition by reader proteins, and the role of trimethyllysine on the nucleosome assembly.

Epigenetic readout of the combinatorial posttranslational modification comprised of trimethyllysine and asymmetric dimethylarginine (H3K4me3R8me2a) takes place via biomolecular recognition of tandem Tudor-domain-containing protein Spindlin1. Through comparative thermodynamic data and molecular dynamics simulations, we sought to explore the binding scope of asymmetric dimethylarginine mimics by Spindlin1. Herein, we provide evidence that the biomolecular recognition of H3K4me2R8me2a is not significantly affected when R8me2a is replaced by dimethylarginine analogues, implying that the binding of K4me3 provides the major binding contribution. High-energy water molecules inside both aromatic cages of the ligand binding sites contribute to the reader–histone association upon displacement by histone peptide, with the K4me3 hydration site being lower in free energy due to a flip of Trp151.

γ-Difluorolysine acts as an excellent lysine mimic and ¹⁹ F NMR probe for examinations of biomedicinally important histone lysine methyltransferases and acetyltransferases.

Five years after the onset of the COVID-19 pandemic, there still is an unmet need for novel antivirals to battle SARS-CoV-2 and other coronaviruses. For this purpose, the development of peptidomimetics against the SARS-CoV-2 main protease (M^pro) and host proteases human cathepsin L (hCTSL) and cathepsin B (hCTSB) is an attractive strategy. These dual-mode antivirals target both viral entry and replication, which could be a suitable alternative to highly specific M^pro and CTS inhibitors. Herein, we examined the inhibitory activity, physicochemical and ADME properties, metabolic stability, and in vivo PK parameters of peptidomimetic inhibitors bearing a potent phenoxymethyl ketone warhead. Our compounds showed nanomolar inhibition of both M^pro and hCTSL/hCTSB and efficiently inhibited SARS-CoV-2 replication in cell culture. Furthermore, we studied metabolism and the impact of coadministration with the CYP-inhibitor ritonavir. Taken together, we report 1 as broad-spectrum coronavirus inhibitor with attractive properties to be pursued in in vivo efficacy studies.