Diamond Concise Annual Review 2021/22

16 17 D I A M O N D L I G H T S O U R C E A N N U A L R E V I E W 2 0 2 1 / 2 2 D I A M O N D L I G H T S O U R C E A N N U A L R E V I E W 2 0 2 1 / 2 2 Biological Cryo-Imaging Group T heBiological Cryo-ImagingGroupbrings together dedicated facilities for X-ray, light, andelectronmicroscopy at DiamondLight Source. The electron Bio-Imaging Centre (eBIC) is the national centre for Cryo-Electron Microscopy (cryo-EM) in the UK and provides a range of capabilities and supporting facilities for cryo-EM and Correlative Light and Electron Microscopy (CLEM). Beamline B24 hosts a full field cryo-transmission X-ray microscope dedicated to biological X-ray imaging and has also established a cryo super resolution fluorescence microscopy facility, which is a joint venture betweenDiamond and the University of Oxford. It provides a unique platformfor correlative light and X-ray microscopy, and cryo-EM. A recent external beamline review rated the B24 facility as excellent and world leading. In particular, the panel commended the beamline team on establishing an internationally unique correlative platform combining two high-end 3D cryo- microscopy techniques (Cryo Soft X-ray Tomography (Cryo-SXT) and Cryo Structured Illumination Microscopy (Cryo-SIM) with user friendly protocols. Recent studies on B24 and eBIC this year include those to understand the detailed 3D structure of human cells, insights into cell division to tackle cancer cells and determining the structure of key proteins involved in the degeneration of nerve fibres. Understanding 3D cell structure It has previouslybeen challenging for researchers toproduce3D, nanometer resolution images of filamentous actin, which is the finest and most dynamic component of the cytoskeleton in cells. Previous imaging of one set of cellular features using one microscope has invariably missed relevant features that can only be captured by different microscopy methods and correlation of imaging data across methods has proved difficult. New techniques have been developed at Diamond to allow researchers to have a greater understanding of the role of actin filaments in many cellular functions such as intracellular transport, membrane remodelling and cell motility. The research team used beamline B24 ensuring the capture of the native ultrastructure in human fibroblasts without the need for chemical or mechanical modification. They then combined two new and powerful imaging techniques (Cryo-SXT and Cryo-SIM) to capture the 3D ultrastructure of the cell and the chemical localisation of filamentous actin, and to correlate these data in 3D. Their findings confirm the applicability of high-resolution cutting- edge 3D cryo-microscopy methods at beamline B24 in the study of biological processes. Koronfel M et al. DOI: 10.1107/S2059798321010329 Determining the structure of cell division mediators Inadequate cell division during mitosis can transform normal growing cells into cancer cells. The protein separase is an important mediator of this complex cell division process and is responsible for the faithful and timely cleavage of the cohesin ring which effectively glues together the sister chromatids inside the cell before mitosis takes place. An international team of researchers using Cryo-EM at eBIC were able to determine the structure of human separase and its two inhibitory binding partners (securin or the CDK1-cyclin B1-CKS1 (CCC) complex). The structure of separase bound to securin confirmed previous studies but the structure of the separase-CCC complex revealed novel and fascinating aspects of separase regulation which mediate binding to specific separase sites. This work highlights the many important roles of separase in cell cycle progression and illustrates the power of Cryo-EM to visualise disordered regions that provide crucial insights into the function of enzyme regulation. This pioneering work may allow new drugs to be sourced to block these sites to prevent the premature chromosome separation which is often observed in cancer cells. Yu J et al. DOI: 10.1038/s41586-021-03764-0 Tackling nerve fibre degeneration SARM1 (sterile alpha and TIR motif 1) is a key player in nerve fibre (axon) degeneration and a promising new therapeutic target for neurological diseases, including peripheral neuropathies and traumatic brain injury. In healthy nerve cells, SARM1 is present but inactive. Disease and injury activate SARM1, which results in rapid breakdown of the‘helper molecule’nicotinamide adenine dinucleotide (NAD + ) and ultimately destruction of the axon. Defining the molecular mechanisms upstream and downstream of SARM1 enzyme activity could yield potential drug targets against neurodegenerative diseases. Using data collected at eBIC and other facilities the researchers were able to determine the structure of SARM1 in its inactive state. They then used X-ray crystallography, to determine a structure of the regulatory domain of Drosophila SARM1 in complex with an allosteric activator. Together these structures explain how the protein maintains an inhibited (off) state and the critical steps required for its activation. These results allowed them to propose a molecular mechanism for SARM1 activation. They also provide a molecular framework for the design of novel drugs targeting a wide range of neurodegenerative diseases. Figley MD et al. DOI: 10.1016/j.neuron.2021.02.009