Studies on phage internal proteins: Isolation of protein-DNA complexes from T2 phages and from phage-infected bacteria

A new procedure has been adapted for the isolation of ³⁵S-labeled internal proteins from T2 phage and from phage-infected bacteria. The isolation of internal proteins from intact phages involved heating with 1% Sarkosyl for 10 min, followed by filtration through Sephadex G-100 and digestion with deoxyribonuclease. Internal proteins were also isolated from phage-infected bacteria by first freezing and thawing in the presence of lysozyme and subsequently treating with detergents. This extraction method has been used to show that internal proteins were transferred into infected cells along with phage DNA. The electrophoretic mobility in polyaclyamide gels was practically identical for internal proteins isolated from T2 phages by either Sarkosyl or the osmotic shock method and for internal proteins transferred into bacteria upon infection. All these preparations contained an identical major ³⁵S-labeled protein and perhaps two additional minor radioactive components.