Fig. 1. Structural architecture of YSD1.

a Vitrification conditions were optimised to trap the flexible Siphoviridae tail tubes as relatively straight segments. Representative cryo-EM image of a YSD1 virion (five imaging sessions). Cryo-EM reconstruction of the YSD1 head (b) and tail tube (c). Major capsid protein (YSD1_17) is shown in blue, auxiliary protein (YSD1_16) is shown in green and one icosahedral asymmetric unit is highlighted in colour (cf. Supplementary Fig. 2 for details). Icosahedral axes are indicated by ellipses, triangles and pentagons for twofold, threefold and fivefold symmetry axes, respectively. Scale bars = 10 nm.