Figure 1.

Cryo-EM of P. aeruginosa TssB1C1 Sheath

(A) EM field of TssB1C1 sheaths embedded in vitreous ice showing tubular assemblies with a single sheath tube highlighted in a yellow box (left). Top views of sheaths showing a cogwheel-like structure with a mix of 12- and 13-fold symmetries (top right). Two-dimensional class averages of TssB1C1 sheaths are presented (bottom right) and appear asymmetric across their meridians, indicating that the dataset is dominated by 13-fold symmetric helical segments. All images are shown with no symmetry imposed. The scale bars represent 290 Å.

(B) Cryo-EM density map of a 162 Å long segment of the TssB1C1 sheath determined at 3.3 Å resolution. Top and side views are shown and the structure is colored according to local resolution, ranging from 3 (blue) to 7 (red) Å.

(C) Ribbon representation of the atomic model of the TssB1C1 heterodimer structure wherein TssB1 is in pink and TssC1 is in purple. Termini are labeled and dashed lines roughly delineate domains 1, 2, and 3.

(D) Close-up of the atomic structure built into the electron density map contoured at 2σ, illustrating the level of detail visible in the cryo-EM reconstruction.

See also Figures S1 and S2.