Lipopolysaccharide Transport Involves Long-Range Coupling between Cytoplasmic and Periplasmic Domains of the LptB2FGC Extractor
Gram-negative bacteria transport lipopolysaccharide (LPS) molecules across their cell envelope to build their outer membrane and create a permeability barrier against antibiotics. This transport is powered by an unusual ATP-binding cassette (ABC) transporter that moves LPS from the inner membrane to a protein bridge that connects to the outer membrane. Lundstedt et al. (e00618-20) show that the activity of this ABC transporter is modulated not only by its ATPase but also by interactions between LPS and sites in the transporter that extend from the inner membrane to the periplasm. These interactions could be targeted to develop antimicrobials that inhibit LPS transport.
A Ribosome-Associated Factor Is Required for Translation of Specific Membrane Proteins in Mycobacteria
LepA is a ribosome-associated GTPase that resembles elongation factors but whose function is unknown. In Mycobacterium smegmatis, loss of LepA results in decreased susceptibility to killing by the antibiotic rifampin. Fishbein et al. (e00604-20) compared the levels of each mRNA and protein in M. smegmatis and find that LepA is required for the efficient translation of a family of porins including MspA. Using a CRISPRi strategy, they showed that the extent of loss of MspA accounted for altered membrane permeability in the LepA mutant. Thus, LepA helps increase the translational efficiency of a subset of critical membrane proteins in mycobacteria.
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