Shuaibing Zhang

Fluorination was used to explore structure–activity relationships of covalent molecular glues for a parasitic enzyme. By shaping the dynamic interplay between ligands and protein surface, fluorination tuned dimer affinity by two orders of magnitude.

While light is essential for many phototrophic organisms, our knowledge of the light-dependent regulation in heterotrophic organisms is scarce. Here, we found that the heterotrophic soil bacterium Pseudomonas protegens differentially accumulated 234 secreted metabolites depending on the light conditions. These metabolites included important antimicrobials such as pyoluteorin, 2,4-diacetylphloroglucinol, pyrrolnitrin, and rhizoxin analogs. Pyoluteorin, for instance, was 140-fold more abundant in the dark, due to a strong upregulation of the transcript of the pyoluteorin biosynthesis gene pltL . We discovered that 2,4-dichlorophloroglucinol (PG-Cl ₂ ), an activator of pyoluteorin biosynthesis, acts as a photoregulator that degrades much faster in the presence of light than in the dark. The resulting higher PG-Cl ₂ levels activate the pltL promoter in the dark. These findings reveal a novel mode of regulation in which light instability of a signal molecule allows the producing organism to sense and transmit light information to regulate the biosynthesis of a secondary metabolite.

Peptidases are indispensable tools in biotechnology and chemical biology. However, the enzyme repertoire for the selective hydrolysis of dl-amide bonds in peptides is small. Here, we describe novel dl-peptidases that mediate complex microbial interactions. These enzymes, Lip3 and Lip7, convert lipopeptides into potent amoebicidal agents via selective dl-peptide bond cleavage. Using structural analyses and mutagenesis, we identified an unusual Ser-Lys-Lys-Tyr catalytic tetrad required for dl-specificity. Despite their high structural similarity, both enzymes show distinct substrate preferences: Lip3 acts primarily as a carboxypeptidase, removing a single C-terminal residue, while Lip7 excises a tripeptide. Although their substrate scopes are broad, they are highly specific with regard to their respective cutting sites. These features make these dl-peptidases powerful tools for elucidating the structure of complex peptide-based natural products, including tensin and WLIP. Overall, this work elucidates the molecular mechanisms of cooperative microbial defense and provides a new enzymatic toolbox for biocatalysis and natural product discovery.

Microbial polyketides represent a structurally diverse class of secondary metabolites with medicinally relevant properties. Aromatic polyketides are produced by type II polyketide synthase (PKS) systems, each minimally composed of a ketosynthase-chain length factor (KS-CLF) and a phosphopantetheinylated acyl carrier protein (holo-ACP). Although type II PKSs are found throughout the bacterial kingdom, and despite their importance to strategic bioengineering, type II PKSs have not been well-studied in vitro. In cases where the KS-CLF can be accessed via E. coli heterologous expression, often the cognate ACPs are not activatable by the broad specificity Bacillus subtilis surfactin-producing phosphopantetheinyl transferase (PPTase) Sfp and, conversely, in systems where the ACP can be activated by Sfp, the corresponding KS-CLF is typically not readily obtained. Here, we report the high-yield heterologous expression of both cyanobacterial Gloeocapsa sp. PCC 7428 minimal type II PKS (gloPKS) components in E. coli, which allowed us to study this minimal type II PKS in vitro. Initially, neither the cognate PPTase nor Sfp converted gloACP to its active holo state. However, by examining sequence differences between Sfp-compatible and -incompatible ACPs, we identified two conserved residues in gloACP that, when mutated, enabled high-yield phosphopantetheinylation of gloACP by Sfp. Using analogous mutations, other previously Sfp-incompatible type II PKS ACPs from different bacterial phyla were also rendered activatable by Sfp. This demonstrates the generalizability of our approach and breaks down a longstanding barrier to type II PKS studies and the exploration of complex biosynthetic pathways.

Major advances over the past decade in the field of ancient DNA are providing access to past paleogenomic diversity, but the diverse functions and biosynthetic capabilities of this growing paleome remain largely elusive. We investigated the dental calculus of 12 Neanderthals and 52 anatomically modern humans ranging from 100,000 years ago to the present and reconstructed 459 bacterial metagenome-assembled genomes. We identified a biosynthetic gene cluster shared by seven Middle and Upper Paleolithic individuals that allows for the heterologous production of a class of previously unknown metabolites that we name “paleofurans.” This paleobiotechnological approach demonstrates that viable biosynthetic machinery can be produced from the preserved genetic material of ancient organisms, allowing access to natural products from the Pleistocene and providing a promising area for natural product exploration.