Figure 4. Failed grgA repression in pGrgA-DOPE is responsible for EB escape in ATC-free cultures of L2/cgad-peig.

(A) Schematic shows mechanism for TetR-mediated grgA transcription repression in L2/cgad-peig cultured in the absence of ATC. (B) Mutations identified in tetR in pGrgA-DOPE recovered from L2/cg-peig EBs formed in the absence of ATC lead to premature translation termination or frameshift. Codon positions in tetR are numbered. Wild-type amino acid sequences are shown in black. Highlighted hyphens and amino acids indicate protein sequence truncation and alteration, respectively. (C) Mutations detected in (B) result in a loss in TetR-mediated grgA repression, leading to GrgA expression in the absence of ATC and consequent EB formation.