Figure 1. Design and validation of the BLaTM assay.

(a) Scheme depicting the main features of the system. (b) Example of dose-response curves where the decrease of E. coli cell density (A₅₄₄) to increasing ampicillin concentration is used to calculate LD₅₀ values. (c) LD₅₀ values derived from part. (b) These values characterize the homotypic interaction of the wild-type (wt) GpA and QSOX2 TMDs and the impact of point mutations (mut). TMDs were inserted into the hybrid proteins at orientations where wild-type/mutant LD₅₀ ratios were maximal (see: Supplementary Fig. S4). (d) Sequence-specific homo- and heterotypic interaction driven by ionizable residues. The LS46 orientation used here leads to superior LD₅₀ values compared to other orientations (not shown). All data were generated using BLaTM 1.1 in E. coli BL21 (b,c) or in E. coli JM83 cells (d) and represent means ± SEM, n = 4 separate transformations. The denomination D₆R₇ corresponds to D₅R₆ previously used³². Single, double, or triple asterisks denote statistical significance at the 0.05, 0.01, or 0.001 confidence levels (relative to the mutants in part (c) or to L19GG in (d)).