Bacterial flagellar motors are diverse rotary machines that require robust mechanical coupling to transmit torque across components with distinct architectures, yet how such coupling is achieved remains poorly understood. Here, we determine near-atomic in situ structures of the periplasmic flagellar motor in the Lyme disease spirochete Borrelia burgdorferi, revealing how an expanded rotor is mechanically coupled to the conserved rod through symmetry breaking and local remodeling of the rotor rod interface. Surprisingly, pentameric FrbA forms a split washer-shaped brace around the rotor rod junction, providing a second layer of mechanical reinforcement. Deletion of frbA destabilizes distal flagellar structures and impairs motility, particularly under increased viscous load. FrbA homologues are broadly distributed across spirochetes, suggesting a conserved mechanism for reinforcing high-torque flagellar motors. Together, these findings reveal how symmetry breaking couples an expanded rotor to a conserved driveshaft, while a molecular split washer reinforces this interface to enable robust torque transmission and motility.

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Proteases must be tightly controlled to clear faulty proteins without damaging cells. Here, authors show that stress-induced membrane insertion activates BepA at stalled outer-membrane protein assembl...

Funded Warwick PhD studying clathrin-coated vesicle formation and lipid nanoparticle drug delivery, with Prof Corinne Smith and Prof Stephen Royle.

Bacterial flagellar motors are diverse rotary machines that require robust mechanical coupling to transmit torque across components with distinct architectures, yet how such coupling is achieved remains poorly understood. Here, we determine near-atomic in situ structures of the periplasmic flagellar motor in the Lyme disease spirochete Borrelia burgdorferi, revealing how an expanded rotor is mechanically coupled to the conserved rod through symmetry breaking and local remodeling of the rotor rod interface. Surprisingly, pentameric FrbA forms a split washer-shaped brace around the rotor rod junction, providing a second layer of mechanical reinforcement. Deletion of frbA destabilizes distal flagellar structures and impairs motility, particularly under increased viscous load. FrbA homologues are broadly distributed across spirochetes, suggesting a conserved mechanism for reinforcing high-torque flagellar motors. Together, these findings reveal how symmetry breaking couples an expanded rotor to a conserved driveshaft, while a molecular split washer reinforces this interface to enable robust torque transmission and motility.

Formation of the activated human spliceosome (Bact) involves major structural rearrangements, leading to the catalytically active U2/U6 RNA core. This process involves at least two intermediates, pre-Bact-1 and pre-Bact-2, and is regulated by CDK11-mediated phosphorylation of the U2 snRNP protein SF3B1. However, the mechanisms of this essential step are poorly understood. Here we present the cryo-EM structure of a spliceosome stalled – by the CDK11 inhibitor OTS964 – in a previously undescribed early-activated state, termed pre-Bact-OTS, shortly after dissociation of U4 snRNP. In pre-Bact-OTS, the U2-SF3B6 protein is retained in a C-terminal region of the super-helical U2-SF3B1 HEAT domain (SF3B1HEAT) that clamps the U2/branch-site helix. In contrast, in pre-Bact-1, SF3B6 is repositioned to SF3B1’s N-terminal HEAT repeats, thereby preventing a steric clash of SF3B6 with PRP8 during the pre-Bact-OTS-to-pre-Bact-1 transition. We infer that the CDK11-mediated phosphorylation of SF3B1 driv

Here, authors solve three cryo-EM structures of EcMscL in two different lipid environments and two distinct conformational states; closed and open-like, guided by EPR. Additional EPR, MD and HDX-MS ex...

PDB-101: Training, Outreach, and Education portal of RCSB PDB

Ionotropic receptors (IRs) are an ancient, massively expanded family of sensory ion channels that mediate chemical, thermal, and hygrosensory detection across invertebrates. Derived from synaptic iono...