Ribosomes after infection with bacteriophage T4 and T7

Summary

The synthesis of E. coli ribosomal proteins ceases after infection with bacteriophages T4 or T7 as does the synthesis of most other host proteins. The shut-off does not affect all ribosomal proteins to the same extent. After T7 infection no new proteins were detected in NH₄Cl-washed ribosomal particles. Bacteriophage T4, however, induces 3–4 new protein bands demonstrated by one-dimensional gel electrophoresis. The appearance of these bands is prevented by the addition of rifampicin at the time of infection but not when rifampicin is added one minute after infection. The NH₄Cl-washed ribosomal particles present at the time of T7 or T4 infection do not show any structural changes by sedimentation, subunit dissociation, or protein analysis on two-dimensional polyacrylamide gels. However, by labeling the T7 infected cells with ³²P-phosphate, it is seen that the ribosomes become phosphorylated. The ³²P-label comigrates with ribosomal proteins. This phosphorylating activity depends on a T7 gene. The T7 protein phosphokinase utilizes ribosomes as phosphate acceptor in vitro. The T7 ribosomes (NH₄Cl-washed) still function in vitro as do ribosomal particles from uninfected cells.