Fig. 6.

Relative positions of the gp15 and gp18 molecules in the extended and contracted T4 tails. The gp15 hexamer is shown in red and the gp18 molecules belonging to the topmost ring of the contractile sheath are shown in green. (a) and (b) show the gp15 and gp18 molecules fitted into the cryo-EM reconstructions of the (a) extended and (b) contracted tails,^5,6 represented by the semitransparent surfaces. (c and d) Side view of the gp15 hexamer and gp18 molecules. (e and f) The gp15 and gp18 molecules viewed from the top of the phage.