Merging Flow Synthesis and Enzymatic Maturation to Expand the Chemical Space of Lasso Peptides.

Many peptidic natural products, such as lasso peptides, cyclic peptides, and cyclotides, are conformationally constrained and show biological stability, making them attractive scaffolds for drug development. Although many peptides can be synthesized and modified through chemical methods, knot-like lasso peptides such as microcin J25 (MccJ25) and their analogues remain elusive. As the chemical space of MccJ25 analogues accessible through purely biological methods is also limited, we proposed a hybrid approach: flow-based chemical synthesis of non-natural precursor peptides, followed by in vitro transformation with recombinant maturation enzymes, to yield a more diverse array of lasso peptides. Herein, we established the rapid, flow-based synthesis of chemically modified MccJ25 precursor peptides (57 amino acids). Heterologous expression of enzymes McjB and McjC was extensively optimized to improve yields and facilitate the synthesis of multiple analogues of MccJ25, including the incorporation of non-canonical tyrosine and histidine derivatives into the lasso scaffold. Finally, using our chemoenzymatic strategy, we produced a biologically active analogue containing three d-amino acids in the loop region and incorporated backbone N-methylations. Our method provides rapid access to chemically modified lasso peptides that could be used to investigate structure-activity relationships, epitope grafting, and the improvement of therapeutic properties.

A Biomimetic Synthesis Elucidates the Origin of Preuisolactone A.

A short, biomimetic synthesis of the fungal metabolite preuisolactone A is described. Its key steps are a purpurogallin-type (5 + 2)-cycloaddition, followed by fragmentation, vinylogous aldol addition, oxidative lactonization, and a final benzilic acid rearrangement. Our work explains why preuisolactone A has been isolated as a racemate and suggests that the natural product is not a sesquiterpenoid but a phenolic polyketide.

Degradation of Protein Kinases: Ternary Complex, Cooperativity, and Selectivity.

In targeted protein degradation of kinases, key discoveries have been made specifically involving selective kinase degradation. Structural and biophysical studies on the ternary complex formation have provided a clear understanding of the basis for achieving degradation selectivity which is important in guiding the design of efficient and selective protein degraders.