Structure of Ergosteryl-Aspartate Synthase Reveals How an Entrapped tRNA Is Used Like a Prosthetic Swinging Arm in the Synthesis of Aminoacylated Sterols

Authors

• Hanako Murayama
• Nathaniel Yakobov
• Nassira Mahmoudi
• Sasha Legrosdidier
• Nicolas Fournier
• Solène Zuttion
• Kanata Matsumoto
• Michihiro Nishimura
• Jingwei Ji
• Bruno Senger
• Laurence Huck
• Howard Gamper, Thomas Jefferson UniversityFollow
• Yoshiaki Kise
• Ralph Kleiner
• Mathieu Frechin
• Ya-Ming Hou, Thomas Jefferson UniversityFollow
• Hubert Becker
• Yuzuru Itoh
• Frédéric Fischer
• Osamu Nureki

Document Type

Article

Publication Date

5-28-2026

Comments

This article is the author’s final published version in Nature Communications, Volume 17, Issue 1, 2026, Article number 4455.

The published version is available at https://doi.org/10.1038/s41467-026-73135-8. Copyright © The Author(s) 2026.

Abstract

Ergosteryl-3β-O-L-aspartate synthase (ErdS) catalyzes tRNA-dependent aspartylation of ergosterol, a lipid essential for fungal cell membrane integrity. However, the functional significance of ergosteryl-aspartate and the molecular mechanisms underlying its synthesis remain unclear. Here, we show that ErdS localization is highly dynamic and that Erg-Asp is required for proper hyphal growth, sporulation, and spore germination, and likely influences stress tolerance. The cryo-electron microscopy structure of ErdS revealed an unprecedented sterol-binding pocket. In addition, the structures in complex with a non-hydrolyzable Asp-N-tRNAAsp show a tRNA-guided intramolecular aminoacyl transfer mechanism between two functional domains of the enzyme. The CCA end of tRNAAsp undergoes a large displacement to reach the aa-tRNA transfer active site, while the tRNA elbow is clamped by a long extension an N-terminal α-helix. The present structural and mutational analyses demonstrate that domain fusion, dynamic repositioning, and tRNA-mediated substrate handover underlie the multifunctional catalytic efficiency of ErdS and participates in Erg-Asp synthesis independently from protein synthesis. These findings elucidate the regulatory mechanism of tRNA-dependent sterol modification and provide insights into fungal membrane dynamics, highlighting potential targets for antifungal therapies.

Recommended Citation

Murayama, Hanako; Yakobov, Nathaniel; Mahmoudi, Nassira; Legrosdidier, Sasha; Fournier, Nicolas; Zuttion, Solène; Matsumoto, Kanata; Nishimura, Michihiro; Ji, Jingwei; Senger, Bruno; Huck, Laurence; Gamper, Howard; Kise, Yoshiaki; Kleiner, Ralph; Frechin, Mathieu; Hou, Ya-Ming; Becker, Hubert; Itoh, Yuzuru; Fischer, Frédéric; and Nureki, Osamu, "Structure of Ergosteryl-Aspartate Synthase Reveals How an Entrapped tRNA Is Used Like a Prosthetic Swinging Arm in the Synthesis of Aminoacylated Sterols" (2026). Department of Biochemistry and Molecular Biology Faculty Papers. Paper 301.
https://jdc.jefferson.edu/bmpfp/301

Creative Commons License

This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.

PubMed ID

42209473

Language

English