Fig. 2

For all panels, measurements for mutants (full circles) are given relative to the TEM-1 allele (open circle), and error bars represent the standard error of the mean (N = 3). The relationship between CTX resistance (x-axis) and relative TEM messenger level (y-axis) is given for the synonymous (a) and non-synonymous mutants (b). The dotted green line indicates TEM-1 expression levels in a, b, e, and f. There does not appear to be a relationship between messenger levels and resistance for either mutation type. The relationship between total (x-axis) and functional TEM protein level (y-axis) is given, for the synonymous TEM mutants (c) and non-synonymous mutants (d). The dotted line is y = x, whereas the solid line is the model-2 regression. For the synonymous mutations, there is a clear relationship between total TEM protein level and measured activity (95% confidence interval of slope: 0.396–0.646), suggesting increased total protein levels correspond well with higher functional protein levels. For the non-synonymous mutations, the relationship is not as evident (95% confidence interval of slope: 0.006–0.690), although some mutations appear to have increases in total and functional protein levels. The relationship between CTX resistance (x-axis) and relative functional TEM protein level (y-axis) is given for the synonymous (e) and non-synonymous mutants (f). The dotted line indicates TEM-1 functional protein levels. For the synonymous mutations, the most resistant alleles have large increases in functional TEM protein levels, whereas some small- and intermediate-level non-synonymous mutations do show increases in functional TEM protein levels similar to those for the synonymous mutations