Fig. 6

Molecular bases for observed phenotypes. A Correlations between experimentally derived mutational scores and sequence-based parameters for the double-site synonymous mutants. Top panel shows these correlations for the N-terminal region. Bottom panel shows these correlations for the middle and C-terminal region. White to red color gradation reflects positive correlation whereas white to blue color gradation reflects negative correlation. Non-significant correlations, i.e., correlations with P > 0.05 are shown with a cross ‘X’ mark. B Elucidating structural properties associated with distinct phenotypic effects. One monomer of CcdB is shown in light grey while residue stretches 52–57 (cyan) and 72–77 (orange) are mapped on the other monomer (tan) of the 3VUB crystal structure. The stretches are part of a β-strand and loop regions. C Comparison of the Hydropathy Index (green) and average ES´^CcdB score (grey) as a function of CcdB position. Hydrophobic residues shown with positive HI values tend to have a higher avgES´^CcdB score than the majority of the mutants