Three-step channel conformational changes common to DNA packaging motors of bacterial viruses T3, T4, SPP1, and Phi29.

The DNA packaging motor of dsDNA bacterial viruses contains a head-tail connector with a channel for the genome to enter during assembly and to exit during host infection. The DNA packaging motor of bacterial virus phi29 was recently reported to use the "One-way revolving" mechanism for DNA packaging. This raises a question of how dsDNA is ejected during infection if the channel acts as a one-way inward valve. Here we report a three step conformational change of the portal channel that is common among DNA translocation motors of bacterial viruses T3, T4, SPP1, and phi29. The channels of these motors exercise three discrete steps of gating, as revealed by electrophysiological assays. The data suggest that the three step channel conformational changes occur during DNA entry process, resulting in a structural transition in preparation for DNA movement in the reverse direction during ejection. Copyright Â