Figure 5: Asymmetric gene regulation by VqmA_Phage and VqmA_Vc.

(A) Fluorescence from PvqmR-mKate2 in ΔvqmA V. cholerae carrying a vector control, vqmA_Vc under its native promoter, or arabinose inducible vqmA_Phage. The medium contained 0.2% arabinose. RFU denotes relative mKate2 fluoresence units. (B) Electrophoretic mobility shift assay with PvqmR DNA (left, white arrowheads) and Pqtip DNA (right, black arrowheads) together with VqmA_Vc, VqmA_Phage, or no protein (denoted -). Proteins used at 130 nM and 16.25 nM (denoted 8x and 1x, respectively). DNA probes = 540 pM. (C) E. coli carrying a plasmid with Pqtip-lux (black) or PvqmR-lux (white) and a second plasmid with either arabinose inducible vqmA_Phage or vqmA_Vc. Medium contained 0.2% arabinose. We estimate that VqmA_Vc binds to its own (PvqmR) promoter 456-fold better than the non-cognate promoter (Pqtip), while VqmA_Phage binds its target promoter (Pqtip) 4.5-fold better than the non-cognate promoter (PvqmR). PvqmR is activated 7-fold more strongly by the cognate VqmA (VqmA_Vc) than by the non-cognate VqmA_Phage. In contrast, Pqtip is activated 278-fold more strongly by the cognate VqmA (VqmA_Phage) than by the non-cognate VqmA_Vc. See Methods for details on quantitative comparisons. (D) Growth of ΔvqmA V. cholerae lysogenized with phage VP882 and either a vector carrying vqmA_Vc (left set of bars) or vqmA_Phage (right set of bars). Black; no arabinose, white; 0.2% arabinose. In A, C, and D, data are represented as mean ± std with n=3 biological replicates. See also Figure S6.