How could CO₂ fixation occur in anaerobic and ancient life? Our new preprint sheds light on catalytic mechanism of the key enzyme CODH/ACS in the Wood-Ljungdahl pathway. Watch the summary movie to see how CO₂ is transformed into acetyl-CoA. Read more: t.ly/u3Ir0

In the proximal conformation we observed that the intrinsically disordered C terminus of FDX2 becomes rigid and interacts with the ISC complex. Thus, a likely role of this isoform-specific element is to mediate the transition to an electron-transfer competent complex. 🧵 5/8

Our structures show that FDX2 can bind in two conformations, ‘distal’ and ‘proximal’ from the ISCU2 FeS assembly site. Only in the proximal conformation FDX2 binds tightly to the complex and is close enough for rapid electron transfer to the FeS assembly site. 🧵 4/8

🎉 Our latest preprint is now online 👉 biorxiv.org/content/10.1101/… Congrats to @RalfSteinhilper who determined #cryoEM structures of the ferredoxin 2-bound core iron-sulfur cluster assembly complex under reducing and turnover conditions at 2 Å resolution. More below! 👇 🧵 1/8

Our proof of principle data show that we can correctly localise abundant elements and perform EELS background subtraction on our reconstructed data. 🎉 🧵 4/6

The reconstruction poses for the EELS data are determined via a reference reconstruction from images from the zero-loss peak region of the energy-loss spectrum. 🧵 3/6

Happy to announce that our efforts to establish elemental mapping for cryo-EM ❄️ by EELS 🌈 are now shared on bioRxiv: biorxiv.org/content/10.1101/… Congratulations to @zoliviapg and co-authors! But wait - Can we map elements in 3D? 🧵👇 1/6

14/A striking feature of SpNOX is how solvent-exposed its outer heme is, in contrast to eukaryotic and cyanobacterial NOXs. We could identify two possible oxygen reduction centers in SpNOX, but mutational analysis did not show a clear decrease in oxidase activity.

13/A Phe397Ala mutant showed an increase in kcat. Further cryo-EM analysis (2.64 Å) showed NADPH moves closer to the FAD, adopting a similar productive state to the one shown for FNR proteins, in which displacement of a terminal Tyr residue is the ‘gate’ for hydride transfer.

12/Surprisingly, even under turnover conditions, the protein did not show clear conformational changes and we could not observe a productive state for hydride transfer. Instead, a conserved C-terminal Phe397 prevented NADPH from approaching FAD close enough.

11/A closer look at the substrate binding site revealed the reason for promiscuity: while eukaryotic NOXs like DUOX1 have two Arg residues interacting with the 2’-phosphate of NADPH, SpNOX has a Tyr residue instead of the second Arg, so it can accomodate NADH as well.