Biology subjects

Low, H. H.

Publications and source records attributed to Low, H. H..

3 recordsLinked to original sources

bioRxiv2023

Mechanism for Vipp1 spiral formation, ring biogenesis and membrane repair

ESCRT-III family proteins build dynamic filaments that remodel membrane. Although the transition of planar filaments into 3D membrane budding structures is fundamental for their function, the geometric changes in polymer architecture driving the transition remain obscure. Here we show how bacterial Vipp1 polymerises into dynamic planar sheets and spirals on membrane. The spirals converge to form a central ring like those known to bud membrane. To probe how Vipp1 morphs between polymers, we determine the architecture of multiple helical filaments. As well as describing filament constriction and membrane tubulation, the geometric relationship between helical and planar lattices enables Vipp1 sheets and spirals to be modelled. Moreover, the helical structures show filaments twisting - a process needed for Vipp1 to transition between planar and 3D architectures. Given the structural conservation between Vipp1 and ESCRT-III, our results may represent the broad changes in geometry required for some ESCRT-III filaments to switch between 2D and 3D forms.

microbiology↗

bioRxiv2020

Bacterial Vipp1 and PspA are members of the ancient ESCRT-III membrane-remodelling superfamily

Membrane remodelling and repair are essential for all cells. Proteins that perform these functions include Vipp1/IM30 in photosynthetic plastids, PspA in bacteria, CdvB in TACK archaea and ESCRT-III in eukaryotes. Here, we show that these protein families are homologous and share a common evolutionary origin. Using cryo-electron microscopy we present structures for Vipp1 rings over a range of symmetries. Each ring is built from rungs that stack and spontaneously self-organise to form domes. Rungs are assembled from a polymer that is strikingly similar in structure to ESCRT-III. A tilt between rungs generates the dome-shaped curvature with constricted open ends and an inner membrane-binding lumen. Overall, our results reveal conserved mechanistic principles that underlie Vipp1, PspA and ESCRT-III dependent membrane remodelling across all domains of life. One sentence summaryEvolutionary and structural analyses of Vipp1/IM30 rings reveal ESCRT-III-like polymers that remodel membranes in bacteria.

microbiology↗

bioRxiv2018

Architecture of a bacterial type II secretion system

Bacterial type II secretion systems (T2SS) translocate virulence factors, toxins and enzymes across the cell outer membrane (OM). An assembled T2SS has not yet been isolated in vitro. Here we use a fusion of negative stain and cryo-electron microscopy (EM) to reveal the core architecture of an assembled T2SS from the pathogen Klebsiella pneumoniae. We show that 7 proteins form a [~]2.5 MDa complex that spans the cell envelope. The outer membrane complex (OMC) includes the secretin PulD with all domains modelled and the pilotin PulS. The inner membrane assembly platform (AP) components PulC, PulE, PulL, PulM and PulN have a relative stoichiometric ratio of 2:1:1:1:1, respectively. The PulE ATPase, PulL and PulM combine to form a flexible hexameric hub. Symmetry mismatch between the OMC and AP is overcome by PulC linkers spanning the periplasm with PulC HR domains binding independently at the secretin base. Our results show the T2SS to have a highly dynamic modular architecture with implication for pseudo-pilus assembly and substrate loading.

microbiology↗