INVITRO PACKAGING OF PLASMID DNA OLIGOMERS BY SALMONELLA PHAGE-P22 - INDEPENDENCE OF THE PAC SITE, AND EVIDENCE FOR THE TERMINATION CUT INVITRO

In vitro packaging experiments with Salmonella phage P22 using artificially ligated plasmid concatemers have shown that the pac site is not necessary for DNA packaging although in vivo this initiation signal is indispensable. This indicates that the phage-coded protein gp3 also executes other important functions during phase maturation in addition to the recognition of pac, or that its site specificity is lost in vitro. It was shown previously that gp3 is necessary for in vitro packaging. It was demonstrated that DNA which is only 74% of headful size cannot be packaged. Oversized DNA, however, is cut in vitro to unit length.