Studies on phage internal proteins. VI. Interaction of bacteriophage T4 internal proteins with T4 DNA in vivo and in vitro.

Internal proteins are basic proteins bound to the DNA of T4 coliphage. Centrifugation in sucrose gradients was employed to isolate DNA-internal proteins complexes formed in vitro. Polyacrylamide gel electrophoresis of radioactive internal proteins in the presence of sodium dodecyl sulfate followed by autoradiography of the gels was used to identify the DNA-bound proteins and to determine their respective abundance in these complexes as well as in the bacteriophage head. The internal proteins were found to bind to the phage DNA (in vitro experiments) at the same ratio as that of internal proteins associated with the viral DNA within the phage head (in vivo binding).