Bacterial flagellar subunits are exported across the cell membrane by the flagellar Type III Secretion System (fT3SS), powered by the proton motive force (pmf) and a specialized ATPase that enables the flagellar export gate to utilize the pmf electric potential (ΔΨ). Export gate activation is mediated by the ATPase stalk, FliJ, but how this process is regulated to prevent wasteful dissipation of pmf in the absence of subunit cargo is not known. Here, we show that FliJ activation of the export gate is regulated by flagellar export chaperones. FliJ binds unladen chaperones and, by using novel chaperone variants specifically defective for FliJ binding, we show that disruption of this interaction attenuates motility and cognate subunit export. We demonstrate in vitro that chaperones and the FlhA export gate component compete for binding to FliJ, and show in vivo that unladen chaperones, which would be present in the cell when subunit levels are low, sequester FliJ to prevent activation of the export gate and attenuate subunit export. Our data indicate a mechanism whereby chaperones couple availability of subunit cargo to pmf-driven export by the fT3SS.
In Escherichia coli AcrB is a major multidrug exporter, which confers the bacterium resistance to many antibiotics with diverse structural and chemical proprieties. Studies have identified three possible tunnels (or channels) within AcrB that different substrates use before reaching the distal pocket, from which they are subsequently extruded. Recently, we reported that mutations in the AcrB gate loop may affect the conformational change kinetics involved in substrate export rather than directly affecting molecular interactions with this loop, and we highlighted the distinct export tunnel preferences between erythromycin and doxorubicin.
National Key Laboratory of Plant Molecular Genetics, Centre for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, China.
Jasmonates (JAs) are a class of oxylipin phytohormones including jasmonic acid (JA) and derivatives that regulate plant growth, development and biotic and abiotic stress. A number of transporters have been identified to be responsible for the cellular and subcellular translocation of JAs. However, the mechanistic understanding of how these transporters specifically recognize and transport JAs is scarce.
Bacteria use a structure called a flagellar filament, made of many subunits, to swim, but it's unclear how they control its length.
Deleting certain genes in polar flagellated bacteria resulted in longer flagellar filaments, suggesting that the FlaG protein helps regulate filament length by interfering with another protein, FliS, in the secretion system.
Both flagellar filaments and injectisome systems appear to have evolved similar protein mechanisms to control the secretion of crucial components, highlighting a convergence in bacterial adaptation strategies.
Lipopolysaccharides (LPS) confer resistance against harsh conditions, including antibiotics, in Gram-negative bacteria. The lipopolysaccharide transport (Lpt) complex, consisting of seven proteins (A-G), exports LPS across the cellular envelope. LptBFG forms an ATP-binding cassette transporter that transfers LPS to LptC.
Guangdong Basic Research Center of Excellence for Ecological Security and Green Development, Key Laboratory for City Cluster Environmental Safety and Green Development of the Ministry of Education, School of Ecology, Environment and Resources, Guangdong University of Technology, Guangzhou 510006, China.
With the increasing demand for plastics, plastic pollution is growing rapidly. A significant amount of plastic has leaked into the environment, leading to severe environmental issues. Biodegradable plastics are considered promising alternatives to conventional durable plastics, and the environmental impacts of biodegradable plastics have received increasing attention.
