Frequency and Fitness Consequences of Bacteriophage Φ6 Host Range Mutations
Panel A: Three host range mutation hotspots (accounting for 86% of all mutations) are highlighted in this linear representation of the 648 amino acid sequence of the Φ6 P3 gene. The remaining 14% of mutations are not shown. Panel B: Space-filling representations of the Φ6 P3 protein are shown as predicted by I-TASSER. Colored regions correspond to the mutation hotspots depicted in Panel A. A putative hydrophobic anchoring domain (HAD) is shown in orange. In our model, the hydrophobic anchoring domain penetrates Φ6's outer lipid membrane to bind inner membrane protein P6. Panel C: Surface electrical charges of E8G mutant contrasted with ancestor. Space-filling representations showing predicted surface electrical charges for the Φ6 E8G host range mutant and its ancestor were estimated using I-TASSER. Positively- and negatively-charged regions are depicted in blue and red respectively. Arrows indicate the predicted location of the mutated 8th residue. The most prominent difference between the mutant and the ancestor is the greater surface positive charge at the presumed host binding domain.