Tat- dependent bundling pilus of a halophilic archaeon assembles by a strand donation mechanism and facilitates biofilm formation

• 成果类型: Article
• 署名作者: Sonani, Ravi R.; Liu, Ying; Xiang, Jialin; Cvirkaite-Krupovic, Virginija; Du, Shishen; Chen, Xiangdong; Krupovic, Mart; Egelman, Edward H.
• 署名单位: University of Virginia; Pasteur Network; Universite Paris Cite; Institut Pasteur Paris; Wuhan University; Wuhan University; Wuhan University
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-14508
• DOI: 10.1073/pnas.2514980122
• 发表日期: 2025-08-05
• 关键词: cell-surface structures; protein secretion; cryo-em; TRANSFORMATION; appendages; alignment; membrane; multiple; bacteria; reveals

摘要

Diverse extracellular filaments present on the surface of archaea mediate multiple key processes, such as motility, adhesion, and biofilm formation. Although several archaeal filament types have been characterized in considerable detail, many remain understudied, particularly those utilizing noncanonical secretion systems. Here, we describe the Tafi bundling pilus that facilitates biofilm formation in the haloarchaeon Natrinema sp. J7-2. Unlike previously characterized archaeal pili, Tafi is secreted via the twin-arginine translocation (Tat) pathway, which transports fully folded proteins across the cytoplasmic membrane. Structural analysis reveals that although Tafi pili assemble via a canonical strand-donation mechanism, the pilin subunit (TafE) adopts a distinct structural topology that sets it apart from the previously characterized Sec-dependent pilins that form bundling pili in archaea. Sequence analyses show that TafE homologs are also present in thermophilic archaea from different phyla, but Tat-signal sequences are exclusive to pilins of halophilic archaea. Nevertheless, we find that Tat signal peptides in haloarchaeal TafE-like pili were exchanged back to the Sec signal peptides on multiple independent occasions. These findings expand our understanding of the diversity and evolution of archaeal extracellular filaments and highlight the Tat pathway as a route for pilus assembly in halophilic archaea.