Synthesis of Nε-acetyl-L-homolysine by the Lossen rearrangement and its application for probing deacetylases and binding modules of acetyl-lysine

Lysine acetylation is a posttranslational protein modification mediating protein-protein interactions by recruitment of bromodomains. Investigations of bromodomains have focused so far on the sequence context of the modification site and acyl-modifications installed at lysine side chains. In contrast, there is only little information about the impact of the lysine residue that carries the modification on bromodomain binding. Here, we report a synthesis strategy for L-acetyl-homolysine from L-2-aminosuberic acid by the Lossen rearrangement. Peptide probes containing acetylated homolysine, lysine, and ornithine were generated and used for probing the binding preferences of four bromodomains from three different families. Tested bromodomains showed distinct binding patterns, and one of them bound acetylated homolysine with similar efficiency as the native substrate containing acetyl-lysine. Deacetylation assays with a bacterial sirtuin showed a strong preference for acetylated lysine, despite a broad specificity for N-acyl modifications.

Peptide-based diagnostic and therapeutic agents: Where we are and where we are heading?

Peptides are increasingly present in all branches of medicine as innovative drugs, imaging agents, theragnostic, and constituent moieties of other sophisticated drugs such as peptide-drug conjugates. Due to new developments in chemical synthesis strategies, computational biology, recombinant technology, and chemical biology, peptide drug development has made a great progress in the last decade. Numerous natural peptides and peptide mimics have been obtained and studied, covering multiple therapeutic areas. Even though peptides have been investigated across the wide therapeutic spectrum, oncology, metabolism, and endocrinology are the most frequent medical indications of them. This review summarizes the current use of and the emerging new opportunities of peptides for diagnosis and treatment of various diseases.

Activity Sensing of Coagulation and Fibrinolytic Proteases

The blood coagulation cascade is a complex physiological process involving the action of multiple coupled enzymes, cofactors, and substrates, ultimately leading to clot formation. Serine proteases have a crucial role, and aberrations in their activity can lead to life-threatening bleeding disorders and thrombosis. This review summarizes the essential proteases involved in blood coagulation and fibrinolysis, the endogenous peptide sequences they recognize and hydrolyze, and synthetic peptide probes based on these sequences to measure their activity. The information in this review can contribute to developing novel anticoagulant therapies and specific substrates for point-of-care diagnosis of coagulation pathologies.

Peptide Probes of Colistin Resistance Discovered via Chemically Enhanced Phage Display

Colistin is an antibiotic of last resort used to treat infections caused by multidrug-resistant Gram-negative bacterial pathogens. The recent surge in reported cases of colistin-resistant infections urgently calls for fast and reliable diagnostic methods, which can be used for the facile detection and proper treatment of these challenging infections. A major mechanism of colistin resistance involves phosphoethanolamine (PE) modification of lipopolysaccharide (LPS), the molecular target of colistin. This LPS modification mechanism has been recently reported to be transferrable via a plasmid-carried mcr-1 gene, which is particularly concerning as it may readily confer colistin resistance to a wide array of bacterial pathogens. To develop molecular tools to allow facile detection of colistin resistance, we have herein enlisted a novel phage library that incorporates dynamic covalent warheads to recognize PE modifications on bacterial cells. Screening of this chemically modified phage library against colistin-resistant pathogens revealed a number of peptide probes that readily differentiate colistin-resistant bacterial strains from their colistin-susceptible counterparts. With a fluorophore label, these peptide probes selectively stain colistin-resistant bacteria at sub-to-low micromolar concentrations. The bacterial staining is minimally inhibited by the presence of serum proteins or even blood serum. Mechanistic studies indicate that our peptide probes bind colistin-resistant bacteria primarily by targeting PE-modified lipids. However, some species-specific features of the cell surface can also contribute to the peptides' association to bacterial cells. Further elucidation of such cell surface features may give molecular probes with improved species and strain specificity, which will enable bacterial infection diagnosis with high precision.