This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: The bacterial flagellum is a motility organelle that enables bacteria to swim and is composed of more than 30 different proteins. Researchers have long sought to understand how this complex nanomachine self-assembles from many parts in the correct order and at the correct positions.
In a study published in Communications Biology, a research team at the University of Osaka revealed the mechanism by which the flagellar motor assembles its bushing around the drive shaft. The LP-ring acts as a molecular bushing surrounding the drive shaft called the rod and supports high-speed rotation of the rod with low friction. During motor assembly, the rod first polymerizes, after which the P-ring forms around a specific part of the rod.
The L-ring subsequently assembles on top of the P-ring, and the completed LP-ring is released from the rod surface to become a bushing. "Because the rod rotates within the mature LP-ring without physical contact, it has long been unclear how the LP-ring is accurately positioned during assembly and how it is later released from the rod," says Tomoko Yamaguchi. "To understand how the LP-ring assembles, we needed structural information on the assembly intermediate." To capture the assembly intermediate, the researchers analyzed a polyrod–P-ring complex (PaPR), in which multiple P-rings assemble around genetically modified elongated rods.
Using electron cryomicroscopy (cryoEM) single-particle analysis, they found that the P-ring initially adopts a slightly elliptical and tilted conformation to increase the contact area with the rod surface to bind to a specific position of the rod. Then, upon formation of the L-ring, steric hindrance arises between the rod and the L-ring, causing the entire LP-ring to detach from the rod surface and become a functional bushing. "Artificially reproducing the autonomous assembly of a complex biomolecular machine remains a major technological challenge," says the senior author Keiichi Namba.
"The bacterial flagellum achieves this process with remarkable precision through self-organization." The newly identified mechanism for constructing and releasing a molecular bearing provides important design principles for self-assembling nanomachines and could contribute to future nanotechnology applications, including highly efficient drug delivery systems (DDSs). Tomoko Yamaguchi et al., Structural insights into the assembly mechanism of the molecular bushing in the bacterial flagellar motor, Communications Biology (2026). DOI: 10.1038/s42003-026-10640-y Journal information: Communications Biology , Science Advances BA art history, MA material culture.
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