Cryoelectron-Microscopic Structure of the pKpQIL Conjugative Pili from Carbapenem-Resistant Klebsiella pneumoniae

Structural analysis of cross α-helical nanotubes provides insight into the designability of filamentous peptide nanomaterials

“…This lability of helical symmetry is common among filamentous peptide assemblies and has been observed even for structures in which the interfacial interactions between protomers are largely conserved. These differences can arise solely as a result of minor changes in interfacial packing orientation between protomers in the filament 10 , 17 , 23 , 71 – 73 .…”

Type IV secretion systems: Advances in structure, function, and activation

“…However, recent structures of two members of the F pilus family (encoded by the pED208 and pOX38 plasmids) solved by single-particle CryoEM revealed not only the expected electron density of the TraA pilin, but also a neighboring density attributed to a phospholipid from the PG (phosphatidylglycerol) family (Figure 3a) (Costa et al, 2016). Similarly, a recent CryoEM structure of an F pilus encoded by K. pneumoniae pKpQIL (Zheng et al, 2020) and a CryoET structure of the F pilus bound with MS2 phage, also shows the presence of both molecular species in the structure (Meng et al, 2019;Zheng et al, 2020). Thus, all F pilus structures solved to date confirm the peculiar arrangement of copious amounts of stoichiometric 1:1 pilin-phospholipid complexes as the building block.…”

“…Recently, our views of how F pili assemble at the cell surface and how they mediate intercellular contacts have been completely reshaped through in situ CryoET studies of the F-encoded T4SS and structural analyses of F pili (Costa et al, 2016;Hu et al, 2019a;Zheng et al, 2020). Analyses of F-encoded structures in the E. coli cell envelope identified several distinct structures, including one interpreted as the translocation channel through which the F plasmid transfer intermediate passes to recipient cells (Figure 1).…”

“…Second, structural resolution of F pili revealed TraA pilin-phospholipid as the fundamental building block, which raises intriguing new questions concerning the pilus biogenesis pathway, the possible functional significance of the PG-lined lumen, and the generality of these findings to other conjugative pili. Third, structural definition of the intrinsically stable OMCCs from the X. citri VirB/VirD4, H. pylori Cag and L. pneumophila Dot/Icm systems revealed that only the latter "expanded" systems display a striking symmetry mismatch between the outer and inner layers (Chung et al, 2019;Costa et al, 2016;Durie et al, 2020;Sgro et al, 2018;Sheedlo et al, 2020;Zheng et al, 2020). This symmetry mismatch is highly curious, especially in view of the fact that "minimized" systems are fully capable of translocating DNA or proteins to other bacteria as well as to eukaryotic cell targets, as best illustrated with the paradigmatic A. tumefaciens VirB/VirD4 T4SS.…”

“…Recently, our views of how F pili assemble at the cell surface and how they mediate intercellular contacts have been completely reshaped through in situ CryoET studies of the F‐encoded T4SS and structural analyses of F pili (Costa et al., 2016; Hu et al., 2019a; Zheng et al., 2020). Analyses of F‐encoded structures in the E .…”