Summary of SUG and PSMR (YkkC/YvdS and YkkD/YvdR) amino acid residue consensus and mean synonymous substitutions (Mean Sd) observed at each position within their overall sequence alignments. Data is shown for SMR members in each panel as follows: A) SUG subclass, B) PSMR subclass members YkkC/YvdS, and C) PSMR subclass members YkkD/YvdR. The amino acid(s) that occurred with the highest frequency at each position within the alignment is indicated on the x-axis below each bar and dashes indicate positions lacking amino acid alignment. Each bar represents the degree of conservation of the listed amino acid(s) below based on its percentage (Consensus %; grey bars) according to the left- hand y-axis. Mean Sd values shown on the right- hand y-axis were calculated from Syn-SCAN pairwise comparisons of Sd values for 20 SMR homologues from each SMR subclass alignment. Mean Sd values, represented as black bars, indicate the level of observed synonymous nucleotide substitutions within the codon for each consensus amino acid listed below.