The Bacteriophage T4 MotB Protein, a DNA-Binding Protein, Improves Phage Fitness.

The lytic bacteriophage T4 employs multiple phage-encoded early proteins to takeover the host. However, the functions of many of these proteins are not known. In this study, we have characterized the T4 early gene , located in a dispensable region of the T4 genome. We show that heterologous production of MotB is highly toxic to , resulting in cell death or growth arrest depending on the strain and that the presence of increases T4 burst size 2-fold. Previous work suggested that affects middle gene expression, but our transcriptome analyses of T4 vs. T4 wt infections reveal that only a few late genes are mildly impaired at 5 min post-infection, and expression of early and middle genes is unaffected. We find that MotB is a DNA-binding protein that binds both unmodified host and T4 modified [(glucosylated, hydroxymethylated-5 cytosine, (GHme-C)] DNA with no detectable sequence specificity. Interestingly, MotB copurifies with the host histone-like proteins, H-NS and StpA, either directly or through cobinding to DNA. We show that H-NS also binds modified T4 DNA and speculate that MotB may alter how H-NS interacts with T4 DNA, host DNA, or both, thereby improving the growth of the phage.