Illustration of the phi29 DNA-packaging motor hexameric structure. (A) Side view
(left) and top view (right) of the phi29 packaging motor and pRNA hexamer. The
30° tilt of the helix of the channel subunit is depicted in both
external and internal views. (Bottom) Side and bottom views of hexameric pRNA
derived from 3WJ crystal structures (Zhang et
al., in press). (B, C) The contact at every 30° for twelve
30° transitions translocates dsDNA one helical turn through the
connector. (D) AFM images of pRNA hexamer. (E) Hexameric motor models of
helicase FtsK and B204 NTPase. (A) and (C), adapted from Zhao et al. (2013), © 2013 with permission
from American Chemical Society; (B) and (D), adapted from Schwartz et al. (2013b), © 2013 with
permission from Elsevier; (E) upper panel, adapted from Happonen et al. (2013), © 2013 with
permission from American Society for Microbiology, and lower panel, adapted from
Massey et al. (2006), © 2006
with permission from Elsevier.