 E. proOmpA pre-incubated at 37oC does not interact with TF. proOmpA1 (5 μM) was preincubated (Buffer D; < 0.2 M urea; 37°C; 10 min) or not (lane 3), prior to addition of the indicated molar excess of TF2 (analyzed as in A). Representative experiment shown; n= 4 biological replicates 