Mutational analysis of the bacteriophage P2 Ogr protein: truncation of the carboxy terminus.

The Ogr protein is a 72-residue, zinc-binding transcription factor essential for activation of late gene expression in bacteriophage P2. Analysis of C-terminal truncated proteins generated by stop codon mutagenesis shows that deletion of residues distal to position 51 had negligible effects on Ogr function. More-extensive deletion resulted in unstable products with severely reduced activity. These results, as well as the effects of other mutations in this region, support the idea that the 21 C-terminal residues are not required for transactivation.