Fig 3.
Secretion efficiencies of clones selected from the Usp45sp silent mutation library and comparison to results from a mathematical model. α-Amylase activity was plotted against the folding energy (ΔG) of the ribosome binding site (RBS) for induction at (A) 0.1 ng/ml, (B) 1 ng/ml, and (C) 10 ng/ml nisin. α-Amylase activity was normalized to the amount secreted by Usp45sp culture induced with 10 ng/ml nisin. ΔGRBS was calculated for the AGGAGG RBS sequence from the mRNA structure with the lowest overall ΔG. The data represent the means ± standard errors of the means (SEM) of the results of three independent experiments. Simulation results show protein secretion levels plotted against ΔG for (D) low (3.2 μM), (E) medium (32 μM), and (F) high (320 μM) mRNA transcript levels. Parameter values used in the model are given in Table S1 in the supplemental material.