Correlation between overexpression levels and degree of growth defects. Average growth defect (LSC) of membrane protein overexpression strains were divided into equally sized bins according to level of protein expression (I, <14; II, 14–34; III, 34–70; IV, 70–120; V, >120 units relative expression level). Asterisks indicate significant (P < 0.001) deviation from the mean growth defect of all investigated strains.