ABSTRACT
The portal channel of double-stranded DNA viruses allows viral genomic DNA to enter the protein procapsid shell during viral maturation and to exit during host infection. The DNA translocase of bacteriophage phi29 was recently reported to use the mechanism of “revolution through a one-way valve” for DNA packaging. This raises a question of how dsDNA is ejected during infection if the channel acts like one-way inward valve. Here, we report three steps of conformational changes in the portal channel that is common to DNA translocases of bacterial viruses T3, T4, SPP1, and phi29. The channels of these motors exercise three discrete steps of gating, as revealed by single-channel electrophysiological assay. It is proposed that the three steps of conformational changes indicate channel structure transition during DNA entry process, in purpose of DNA ejection in phage.
