FIG 21.

Role of the flexible inner channel loop of phage portal proteins in DNA one-way traffic. (A) Flexible loops within the phi29 (left) and SPP1 (right) connector channels function to interact with dsDNA, facilitating DNA to move forward but blocking reversal of DNA during DNA packaging. (B) Demonstration of one-way traffic of dsDNA through wild-type connectors using a ramping potential or a switching polarity (right). (C) ssDNA is translocated via two-way traffic with a loop-deleted connector. (Adapted from reference 13.)