Glutathione S-transferase-sspA fusion binds to E. coli RNA polymerase and complements delta sspA mutation allowing phage P1 replication.

Bacteriophage P1 is unable to form plaques on E. coli hosts lacking a functional sspA gene. However, sspA mutants can be infected by P1, resulting in the synthesis of P1 early gene products and accumulation of P1 DNA, but without P1 late gene product formation or host lysis. Overexpression of the stringent starvation protein (SspA) as a glutathione-S-transferase fusion results in complementation of the sspA mutation and production of viable viral particles as in sspA+ strains. This suggests that the GST-SspA protein functions in vivo in a similar manner as native SspA with respect to P1 replication. Here, evidence is presented that shows that SspA binds to RNA-polymerase. This supports the notion that SspA is involved in P1 replication since it is known that P1 requires host RNA-polymerase activity to replicate and this suggests a mechanism by which P1 redirects E. coli RNA-polymerase specificity from P1 early to P1 late genes.