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Nonribosomal peptide synthetases (NRPSs) are very large proteins that produce small peptide molecules with wide-ranging biological activities, including environmentally friendly chemicals and many widely used therapeutics. NRPSs are macromolecular machines, with modular assembly-line logic, a complex catalytic cycle, moving parts and many active sites. In addition to the core domains required to link the substrates, they often include specialized tailoring domains, which introduce chemical modifications and allow the product to access a large expanse of chemical space. It is still unknown how the NRPS tailoring domains are structurally accommodated into megaenzymes or how they have adapted to function in nonribosomal peptide synthesis. Here we present a series of crystal structures of the initiation module of an antibiotic-producing NRPS, linear gramicidin synthetase. This module includes the specialized tailoring formylation domain, and states are captured that represent every major step of the assembly-line synthesis in the initiation module. The transitions between conformations are large in scale, with both the peptidyl carrier protein domain and the adenylation subdomain undergoing huge movements to transport substrate between distal active sites. The structures highlight the great versatility of NRPSs, as small domains repurpose and recycle their limited interfaces to interact with their various binding partners. Understanding tailoring domains is important if NRPSs are to be utilized in the production of novel therapeutics.

Background Inappropriate prescribing increases patient illness and death owing to adverse drug events. The inclusion of genetic information into primary care medication practices is one solution. Our aim was to assess the ability to obtain and genotype saliva samples and to determine the levels of use of a decision support tool that creates medication options adjusted for patient characteristics, drug-drug interactions and pharmacogenetics. Methods We conducted a cohort study in 6 primary care settings (5 family practices and 1 pharmacy), enrolling 191 adults with at least 1 of 10 common diseases. Saliva samples were obtained in the physician's office or pharmacy and sent to our laboratory, where DNA was extracted and genotyped and reports were generated. The reports were sent directly to the family physician/pharmacist and linked to an evidence-based prescribing decision support system. The primary outcome was ability to obtain and genotype samples. The secondary outcomes were yield and purity of DNA samples, ability to link results to decision support software and use of the decision support software. Results Genotyping resulted in linking of 189 patients (99%) with pharmacogenetic reports to the decision support program. A total of 96.8% of samples had at least 1 actionable genotype for medications included in the decision support system. The medication support system was used by the physicians and pharmacists 236 times over 3 months. Interpretation Physicians and pharmacists can collect saliva samples of sufficient quantity and quality for DNA extraction, purification and genotyping. A clinical decision support system with integrated data from pharmacogenetic tests may enable personalized prescribing within primary care. Trial registration: ClinicalTrials.gov, NCT02383290.