Tight- packing of large pilin subunits provides distinct structural and mechanical properties for the Myxococcus xanthus type IVa pilus

• 成果类型: Article
• 署名作者: Treuner-Lange, Anke; Zheng, Weili; Viljoen, Albertus; Lindow, Steffi; Herfurth, Marco; Dufrene, Yves F.; Sogaard-Andersen, Lotte; Egelman, Edward H.; Hultgren, Scott
• 署名单位: Max Planck Society; University of Virginia; Universite Catholique Louvain
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-9552
• DOI: 10.1073/pnas.2321989121
• 发表日期: 2024-04-23
• 关键词: pseudomonas-aeruginosa; cryoelectron microscopy; motility systems; adhesion forces; proteins; reveals; retraction; binding

摘要

Type IVa pili (T4aP) are ubiquitous cell surface filaments important for surface motility, adhesion to surfaces, DNA uptake, biofilm formation, and virulence. T4aP are built from thousands of copies of the major pilin subunit and tipped by a complex composed of minor pilins and in some systems also the PilY1 adhesin. While major pilins of structurally characterized T4aP have lengths of <165 residues, the major pilin PilA of Myxococcus xanthus is unusually large with 208 residues. All major pilins have a conserved N-terminal domain and a variable C-terminal domain, and the additional residues of PilA are due to a larger C-terminal domain. We solved the structure of the M. xanthus T4aP (T4aP(Mx)) at a resolution of 3.0 angstrom using cryo-EM. The T4aP(Mx) follows the structural blueprint of other T4aP with the pilus core comprised of the interacting N-terminal alpha 1-helices, while the globular domains decorate the T4aP surface. The atomic model of PilA built into this map shows that the large C-terminal domain has more extensive intersubunit contacts than major pilins in other T4aP. As expected from these greater contacts, the bending and axial stiffness of the T4aP(Mx) is significantly higher than that of other T4aP and supports T4aP-dependent motility on surfaces of different stiffnesses. Notably, T4aP(Mx) variants with interrupted intersubunit interfaces had decreased bending stiffness, pilus length, and strongly reduced motility. These observations support an evolutionary scenario whereby the large major pilin enables the formation of a rigid T4aP that expands the environmental conditions in which the T4aP system functions.