Diamond Concise Annual Review 2020/21

Macromolecular Crystallography Group B iological interactions underpin and can undermine the processes of life, as exemplified this year by the SARS-CoV-2 pandemic. The technique of Macromolecular Crystallography (MX) uses X-rays to reveal the details of biological molecules at atomic and temporal scales and is an enabler in our understanding of the processes and interactions of life. Seven beamlines (I03, I04, I04-1, I23, I24, VMXi and VMXm), alongside the XChem fragment screening facility, the UK X-ray Free Electron Laser (XFEL) Hub and the Membrane Protein Laboratory (MPL) at Diamond Light Source are dedicated to exploiting the technique of MX for the benefit of the worldwide structural biology community. Some of the exciting studies taking place in the MX Group this year have included new insights into key enzymes that can degrade plastics, improved understanding of an anti-tuberculosis therapy, and discoveries in our gut bacteria which could lead to valuable new diagnostic tests for various diseases. Engineering enzymes to recycle plastics An international team is continuing its pioneering work on discovery and engineering of enzymes that can help break down plastics for recycling. Previous studies at Diamond Light Source focused on characterising the structure and function of the enzyme PETase, which is able to break down one of the most commonly-polluting plastics, polyethylene terephthalate (PET), that is used for bottles and textiles. The enzyme was isolated from the bacterium Ideonella sakaiensis , originally discovered ‘feeding’ on plastic waste in a Japanese recycling centre. This new study, carried out on beamline I03, studied a partner enzyme called MHETase which is secreted from the same bacterium. The structures collected from the beamline are at the highest resolution available and provide a detailed insight into the MHETase enzyme. Combined with detailed bioinformatics, biochemistry and molecular simulations, they show a highly synergistic relationship between the PETase and MHETase enzymes. The team investigated if tethering the proteins together could improve the breakdown and demonstrated that this was significantly faster than PETase alone or a PETase- MHETase cocktail.This ongoing research effort adds significantly to the global focus on finding low-energy methods to recycle plastics and to reduce our requirements for fossil resources. Knott B. C. et al. DOI: 10.1073/pnas.2006753117 Developing new anti-tuberculosis drugs An international group of Chinese, Australian and UK researchers used beamline I04-1 at Diamond Light Source to determine the detailed crystal structure of a mycobacterial complex that provides fresh understanding of the biochemical function of proteins associated with tuberculosis (TB). The TB bacterium Mycobacterium tuberculosis is able to build a complex cell wall to protect and support itself. This cell wall has been a key target for anti-TB drugs. For example, the front-line anti-TB drug ethambutol inhibits synthesis of the bacterial cell wall by targeting certain key proteins. Although this drug has been in use for 50 years, its precise mode of action remains unclear. The team focused on the action of the EmbC protein which plays a key role in synthesis of the bacterial cell wall. They discovered compelling new information on its binding capacity, showing that ethambutol functions by competing with the substrates for binding to EmbC. These results provide a structural basis for understanding the biochemical function and inhibition of EmbC and for the exciting development of new anti-TB agents. Zhang L. et al. DOI: 10.1126/science.aba9102 Developing diagnostic tests fromgut bacteria New studies on gut flora may have important implications for human health and disease including greater understanding of certain cancers and diabetes. The microorganisms that live in the human gut have a profound impact on our health. The microbes living in intestinal mucus, a complex network of proteins and attached sugars, act as‘gatekeepers’by maintaining gut barrier function. However, the mechanisms by which they interact with the host remain largely unknown. Researchers investigated Ruminococcus gnavus , a common resident of the human gut that has a role in health and disease. They investigated its potential to process the sugar fucose using enzymes called fucosidases. They also explored the pool of fucosidases produced by different R. gnavus strains. Using the Versatile Macromolecular Crystallography in situ (VMXi) beamline at Diamond Light Source allowed the team to track their crystallisation experiments in real-time.They were also able to test crystal diffraction quickly and easily, rapidly optimising crystallisation conditions to produce consistent, high-quality protein crystals for X-ray diffraction experiments on MX beamlines I03 and I04. This new understanding of fucosidases may allow scientists to design new diagnostic assays for diabetes and a number of cancers. Wu H. et al. DOI: 10.1007/s00018-020-03514-x 14 15 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 0 / 2 1 Science Highlights