Atomic-scale structural analyses performed at Berkeley Lab’s Advanced Light Source (ALS) are helping scientists understand the inner workings of the enzyme “assembly lines” that microbes use to produce an important class of compounds, many of which have uses as antibiotics, antifungals, and immunosuppressants.

These cellular machines, known as nonribosomal peptide synthetases (NRPSs), are large, multi-enzyme clusters that synthesize compounds by passing a precursor molecule from one module to the next, with each “station” catalyzing a change in the molecule. In the past decade, researchers have learned a great deal about how individual NRPS modules work, but an understanding of how the assembly lines function as a whole has been lacking. In the hopes of eventually engineering custom NRPSs to make new and improved medicines, a team led by McGill University began investigating the bacterial NRPS that synthesizes the antibiotic gramicidin.

The scientists used the SIBYLS X-ray scattering beamline at the ALS to validate X-ray crystallography and small-angle X-ray scattering performed at the Canadian Light Source in Saskatchewan and the Advanced Photon Source at Argonne National Laboratory. The results, published in Science, show that the modules are surprisingly physically flexible, and that the assembly line can function in many different arrangements.

Gregory Hura, a Berkeley Lab biophysicist on the SIBYLS team and head of the Structural Biology Department in the Molecular Biophysics & Integrated Bioimaging Division, notes that the analytic capabilities of the beamline are helping decode the functionality of many important large molecules. “There is no surprise that macromolecules, responsible for the complex activities of life, are dynamic, modular, and multifaceted – but our appreciation for those dynamics has been hindered by a lack of modalities for sensing them. The newly upgraded SIBYLS beamline provides unique insights that complement crystallography and electron microscopy, and together, these technologies are helping us develop new medicines.”