Cryo-EM Resolves Molecular Recognition Of An Optojasp Photoswitch Bound To Actin Filaments In Both Switch States

Actin is essential for key processes in all eukaryotic cells. Cellpermeable optojasps provide spatiotemporal control of the actin cytoskeleton, confining toxicity and potentially rendering F-actin druggable by photopharmacology. Here, we report cryo electron microscopy (cryo-EM) structures of both isomeric states of one optojasp bound to actin filaments. The high-resolution structures reveal for the first time the pronounced effects of photoswitching a functionalized azobenzene. By characterizing the optojasp binding site and identifying conformational changes within F-actin that depend on the optojasp isomeric state, we refine determinants for the design of functional F-actin photoswitches.

TranSPHIRE: automated and feedback-optimized on-the-fly processing for cryo-EM

Single particle cryo-EM requires full automation to allow high-throughput structure determination. Although software packages exist where parts of the cryo-EM pipeline are automated, a complete solution that offers reliable on-the-fly processing, resulting in high-resolution structures, does not exist. Here we present TranSPHIRE: A software package for fully-automated processing of cryo-EM datasets during data acquisition. TranSPHIRE transfers data from the microscope, automatically applies the common pre-processing steps, picks particles, performs 2D clustering, and 3D refinement parallel to image recording. Importantly, TranSPHIRE introduces a machine learning-based feedback loop to re-train its picking model to adapt to any given data set live during processing. This elegant approach enables TranSPHIRE to process data more effectively, producing high-quality particle stacks. TranSPHIRE collects and displays all metrics and microscope settings to allow users to quickly evaluate data during acquisition. TranSPHIRE can run on a single work station and also includes the automated processing of filaments.

cryoEM-Guided Development of Antibiotics for Drug-Resistant Bacteria

While the ribosome is a common target for antibiotics, challenges with crystallography can impede the development of new bioactives using structure-based drug design approaches. In this study we exploit common structural features present in linezolid-resistant forms of both methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE) to redesign the antibiotic. Enabled by rapid and facile cryoEM structures, this process has identified (S)-2,2-dichloro-N-((3-(3-fluoro-4-morpholinophenyl)-2-oxooxazolidin-5-yl)methyl)acetamide (LZD-5) and (S)-2-chloro-N-((3-(3-fluoro-4-morpholinophenyl)-2-oxooxazolidin-5-yl)methyl) acetamide (LZD-6), which inhibit the ribosomal function and growth of linezolid-resistant MRSA and VRE. The strategy discussed highlights the potential for cryoEM to facilitate the development of novel bioactive materials.