Structural and mechanistic insights into the fungal glycosylphosphatidylinositol mannosyltransferase I complex

• 成果类型: Article
• 署名作者: Liu, Jia; Yang, Yizheng; Tan, Yi; Hua, Zhengkang; Hu, Xinlin; Ding, Xuyang; Yang, Ping; Ke, Yan; Zhang, Zhentao; Li, Tianlu; Peng, Peng; Zhang, Min; Yu, Hongjun
• 署名单位: Huazhong University of Science & Technology; Huazhong University of Science & Technology; Huazhong University of Science & Technology; Huazhong University of Science & Technology; Shandong University; Huazhong University of Science & Technology
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.2617140123
• 发表日期: 2026-09-15
• 页码: e2617140123
• 关键词: GPI mannosyltransferase; glycosylphosphatidylinositol; GPI anchor; glycobiology; antifungal drug; CELL-WALL INTEGRITY; saccharomyces-cerevisiae; 1ST MANNOSYLTRANSFERASE; endoplasmic-reticulum; biosynthetic-pathway; ANCHOR BIOSYNTHESIS; TRYPANOSOMA-BRUCEI; PIG-M; GPI; phosphatidylinositol

摘要

Glycosylphosphatidylinositol (GPI) anchoring shapes eukaryotic cell-surface architecture and represents an attractive pathway for antifungal intervention. The first committed mannosylation step in GPI biosynthesis is catalyzed by GPI mannosyltransferase I (GPI-MT-I), a membrane-embedded enzyme complex essential for fungal cell-wall integrity and virulence. Despite its therapeutic potential, the molecular basis and chemical mechanism of this lipid-dependent glycosyltransferase have remained unclear. Here, we combine cryoelectron microscopy, chemical synthesis, and functional analyses to define the architecture, substrate recognition, and catalytic mechanism of fungal GPI-MT-I, the Gpi14-Pbn1 heterodimer. We captured catalytically distinct states of fungal GPI-MT-I, including a ternary complex simultaneously bound to dolichol-phosphate-mannose and GlcN-(acyl)phosphatidylinositol. These reveal a membrane-embedded reaction chamber containing a continuous substrate-binding tunnel, in which two amphipathic lipid substrates are positioned in a head-to-head configuration for glycosyl transfer. Structural and mutational analyses establish GPI-MT-I as a GT-C-fold inverting glycosyltransferase and support a concerted SN2-like mechanism centered on the conserved catalytic aspartate Asp38. Comparative analyses reveal pronounced fungal-specific structural features with therapeutic potential, explaining the functional incompatibility across species. These findings provide a molecular and chemical blueprint for lipid-linked glycosyl transfer in membranes and a foundation for structure-guided antifungal drug development.