Fig. 2. Cryo-EM data for hybrid structure calculation provides global and local information.

a 3.5–6 Å cryo-EM map of the tail tube of SPP1 consisting of polymerized gp17.1 subunits does not only allow to deduce symmetry restraints but also limits the position of all atoms within the density. Rings with a thickness of 38.5 Å (as represented by the straight arrows) stack onto each other with a rotation of 21.9° (as represented by the bent arrow). b–d Local resolution of the cryo-EM map increases going from outer to the inner surface of the tail tube (as represented by the color gradient). e The inner region of the map reveals a highly resolved β-barrel and allows for the positioning of bulky sidechains as exemplified for Tyr67 and Tyr68 (f). The direction of the tail structure is baseplate upwards.