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The main protease, a key enzyme of SARS-CoV-2, can protect itself from oxidative damage. Here, Reinke, Schubert, and colleagues used XFEL radiation to image the enzyme, revealing the disulfide and NOS/SONOS bonds that form in response to oxygen.

The European X-ray free-electron laser (EuXFEL) in Hamburg is the first XFEL with a megahertz repetition rate. Here the authors present the 2.9 Å structure of the large membrane protein complex Photosystem I from T. elongatus that was determined at the EuXFEL.

European XFEL allows investigation of the picosecond time range in the photocycle of photoactive yellow protein.

For conventional three-dimensional microcrystal electron diffraction (3D ED/MicroED), a crystal is slowly rotated under an electron beam, leading to inevitable accumulation of radiation damage during data collection. In this work, the authors present a serial electron diffraction method, where still diffraction patterns from many protein nanocrystals are rapidly recorded and merged, which minimises radiation damage and only requires a slightly modified standard scanning transmission electron microscope.

Here, the reaction of the suicide inhibitor sulbactam with the M. tuberculosis β-lactamase (BlaC) is investigated with time-resolved crystallography. Singular Value Decomposition is implemented to extract kinetic information despite changes in unit cell parameters during the time-course of the reaction.

Free-electron lasers are capable of high repetition rates and it is assumed that protein crystals often do not survive the first X-ray pulse. Here the authors address these issues with a demonstration of multi-hit serial crystallography in which multiple FEL pulses interact with the sample without destroying it.

Time-resolved crystallography (TRX) is used for monitoring only small conformational changes of biomacromolecules within the same lattice. Here, the authors report the interplay between synchronous molecular rearrangements and lattice phase transitions in RNA crystals, providing the basis for the investigation of large conformational changes using TRX.

Time-resolved serial femtosecond crystallography is used to reveal the structural changes that stabilize the charge-separation steps of electron-transfer reactions in the photosynthetic reaction centre of Blastochloris viridis on a timescale of picoseconds.

Diacylglycerol kinase is a small bacterial membrane-bound trimer that catalyses diacylglycerol conversion to phosphatidic acid. Here, the authors solve the crystal structure of the kinase bound to a lipid substrate and an ATP analogue, and show that the active site arose through convergent evolution.

There is a need for more robust sample delivery methods for serial crystallography. Here the authors present the design and characterization of ultracompact 3D microfluidic devices that can be printed, which require less sample, have a lower background signal and allow 3D mixing for time resolved experiments.

The new European X-Ray Free-Electron Laser (EuXFEL) is the first XFEL that generates X-ray pulses with a megahertz inter-pulse spacing. Here the authors demonstrate that high-quality and damage-free protein structures can be obtained with the currently available 1.1 MHz repetition rate pulses using lysozyme as a test case and furthermore present a β-lactamase structure.

G protein-coupled receptors are a large family of signalling proteins that mediate cellular responses primarily via G proteins or arrestins, and they are targets of one-third of the current clinically used drugs; here, an active form of human rhodopsin bound to a pre-activated form of the mouse visual arrestin-1 is determined, revealing unique structural features that may constitute essential elements for arrestin-biased signalling.

Serial femtosecond crystallography of the human δ-opioid receptor in complex with an endomorphin-derived peptide reveals interactions that are important for understanding the pharmacology of opioid peptides and developing analgesics with reduced side effects.

Crystal lattice disorder, which gives rise to a continuous diffraction pattern, is exploited to determine the structure of the integral membrane protein complex photosystem II to a higher resolution than could be achieved using Bragg diffraction alone.

Boronate-based ß-lactamase inhibitors play an important role in treating multidrug-resistant bacteria infection, however, the molecular mechanism of inhibition remains unclear. Here, the authors use time-resolved serial crystallography to investigate the binding process by using boric acid as a model against β-lactamase CTX-M-14, revealing the binding to the active site serine within 80–100 ms, a subsequent 1,2-diol boric ester formation with glycerol within 100–150 ms, as well as the displacement of the sulfate anion in the active site.

High-resolution, low-dose images of biological objects were obtained in a new method using photons of 60 keV. The dose was thousands of times lower than conventional methods, overcoming the previous limitations set by radiation damage to the sample.

Three natural phenolic compounds are found to bind to an allosteric site in SARS-CoV-2 papain-like protease and exhibit antiviral activity in vitro, showing potential as starting scaffolds for drug design.

Ayan et al. report two structures of the protein streptavidin - one at ambient temperature determined using serial femtosecond crystallography and a second one determined at cryogenic temperature. These results provide insights into the structural dynamics of apo streptavidin and reveal a cooperative allostery between monomers for binding to biotin, and the findings are supported by GNM analysis.