FIG. 3.

Protein-protein interactions between TcpH and other Tcp proteins. β-Galactosidase assays were performed in duplicate on three separate cultures. Samples were derived from E. coli BTH101 cells cotransformed with pUT18C and pKT25 that were fused to DNA sequences encoding TcpH (H) and the other Tcp derivatives (A, B, C, etc.) as shown. As negative controls, BTH101 cells were cotransformed with a vector expressing the test protein fused to either the T25 or T18 domain and a corresponding control plasmid (pUT18C or pKT25, respectively). The dashed line represents the highest level of β-galactosidase activity from the negative controls. Statistical analysis was carried out using the Student's t test after analysis of variance, as indicated by an asterisk (P < 0.05 compared to results for the negative control).