Botte, MathieuNi, DongchunSchenck, StephanZimmermann, IwanChami, MohamedBocquet, NicolasEgloff, PascalBucher, DenisTrabuco, MatildeCheng, Robert K. Y.Brunner, Janine D.Seeger, Markus A.Stahlberg, HenningHennig, Michael2022-04-272022-04-272022-04-272022-04-0510.1038/s41467-022-29459-2https://infoscience.epfl.ch/handle/20.500.14299/187478Lipopolysaccharides are major constituents of the extracellular leaflet in the bacterial outer membrane and form an effective physical barrier for environmental threats and for antibiotics in Gram-negative bacteria. The last step of LPS insertion via the Lpt pathway is mediated by the LptD/E protein complex. Detailed insights into the architecture of LptDE transporter complexes have been derived from X-ray crystallography. However, no structure of a laterally open LptD transporter, a transient state that occurs during LPS release, is available to date. Here, we report a cryo-EM structure of a partially opened LptDE transporter in complex with rigid chaperones derived from nanobodies, at 3.4 Å resolution. In addition, a subset of particles allows to model a structure of a laterally fully opened LptDE complex. Our work offers insights into the mechanism of LPS insertion, provides a structural framework for the development of antibiotics targeting LptD and describes a highly rigid chaperone scaffold to enable structural biology of challenging protein targets.text::journal::journal article::research article