Researchers from the University of Liverpool, Japan, and Argentina have captured atomic‑resolution images of an important copper-containing enzyme using advanced X-ray Free Electron Laser (XFEL) technology at SACLA in Japan.
XFEL technology generates ultra-bright, ultra-short X-ray pulses, enabling atomic-scale imaging and real-time observation of chemical, biological, and physical processes.
The international team - led by Dr Svetlana Antonyuk and Professor Samar Hasnain at the University of Liverpool, Professor Takehiko Tosha at the University of Hyogo, and Dr Masaki Yamamoto at RIKEN SPring-8 - studied a protein that plays a key role in the global nitrogen cycle. This protein converts nitrite, an essential nitrogen intermediate, into nitric oxide gas.
The new details reveal how an enzyme called copper nitrite reductase (CuNiR) from three different organisms converts nitrite to nitric oxide gas, using an electron and a proton - a vital process for both biology and the environment.
The results resolve a long‑standing debate about whether the enzyme works through an ordered or random‑sequential mechanism. The study shows that the reaction follows an ordered sequence, clarifying how electrons, substrate molecules, and protons are coordinated.
Beyond its biological significance, the research demonstrates how combining XFEL technology with advanced structure‑refinement software (SHELXL) can resolve biomolecules at individual‑atom resolution.
Dr Svetlana Antonyuk said: "The ability of XFEL to deliver higher energy X-rays >13 keV of around ten femtosecond pulses can be successfully harnessed to provide atomic resolution structures that are free from X-ray induced redox or chemical changes in the biological system under investigation"
Professor Samar Hasnain said: "We have dedicated this paper to Professor George Sheldrick (1942-2025), whose development of the SHELXL refinement method transformed structural analysis. Our work is the first to apply this approach to atomic‑resolution macromolecular structures obtained using an XFEL."
The results of this study are published in the scientific journal Nature Communications.
