Apramycin is aclinically promising aminoglycoside antibiotic (AGA). To date,m echanisms underlying the biosynthesis and self-resistance of apramycin remain largely unknown. Here we report that apramycin biosynthesis proceeds through unexpected phosphorylation, deacetylation, and dephosphorylation steps,i nw hich an ovel aminoglycoside phosphotransferase (AprU), ap utative creatinine amidohydrolase (AprP), and an alkaline phosphatase (AprZ) are involved. Biochemical characterization revealed that AprU specifically phosphorylates 5-OH of ap seudotrisaccharide intermediate,w hose N-7' acetyl group is subsequently hydrolyzed by AprP.A prZ is located extracellularly where it removes the phosphate group from ap seudotetrasaccharide intermediate,leading to the maturation of apramycin. Intriguingly,7'-N-acetylated and 5-O-phosphorylated apramycin that were accumulated in DaprU and DaprZ respectively exhibited significantly reduced antibacterial activities,i mplying Streptomyces tenebrarius employs C-5 phosphorylation and N-7' acetylation as two strategies to avoid auto-toxicity.S ignificantly,t his study provides insight into the design of new generation AGAs to circumvent the emergence of drugresistant pathogens.

Non-Ribosomal Peptide Synthetases (NRPSs) assemble a diverse range of natural products with important applications in both medicine and agriculture. They consist of several multienzyme subunits that must interact with each other in a highly controlled manner to facilitate efficient chain transfer, thus ensuring biosynthetic fidelity. Several mechanisms for chain transfer are known for NRPSs, promoting structural diversity. Herein, we report the first biochemically characterized example of a type II thioesterase (TEII) domain capable of catalysing aminoacyl chain transfer between thiolation (T) domains on two separate NRPS subunits responsible for installation of a dehydrobutyrine moiety. Biochemical dissection of this process reveals the central role of the TEII-catalysed chain translocation event and expands the enzymatic scope of TEII domains beyond canonical (amino)acyl chain hydrolysis. The apparent co-evolution of the TEII domain with the NRPS subunits highlights a unique feature of this enzymatic cassette, which will undoubtedly find utility in biosynthetic engineering efforts.

Threat or treat? While pathogenic bacteria pose significant threats, they also represent a huge reservoir of potential pharmaceuticals to treat various diseases.

A novel light-up NIR fluorescence probe was developed and used for tumor and drug-induced liver injury imaging in vivo.

The dual modal imaging probe H-dot was prepared for in vivo NIR-II/MR imaging of orthotopic U87MG glioblastoma xenografts.