Illustration of the mechanism of dsDNA twisting during DNA packaging due to conformational changes of the Phi29 connector channel. (A) Discrete three step-wise conformational changes of Phi29 connector channel were detected by single channel conductance assay with the connector embedded in lipid bilayer. The external view of the crystal structure of the connector channel is shown on the right. (B) The C-terminal of the connector inside the procapsid is more static than the external N-terminal. As a result, the N-terminal of the connector may shift leftwards during the DNA packaging, leading to the clockwise twist of the DNA that aligns within the connector channel wall.