(B) Linear regression applied to predict the synthetic promoter activity based on individual motif features (intra-architectural mutations). The measured expressions (on the y-axis) for 6 tested core promoter sequences with combinatorial motif mutations compared to the predicted expressions (on the x-axis) from the linear regression (log2 scale). Red solid line: y = x; red dashed lines: y = x ± 3×SD, where SD denotes the median of all standard deviations over all measured synthetic promoter constructs. It is an estimate for the noise in the expression measurements. The linear regression model can explain on average 88% of the variance in expression (average r = 0.88). 