Electrophoretic migration of representative wild-type and mutant OmpA proteins on 12% SDS PAGE gels. Samples were loaded without heating (U) and after heating in 2% SDS in a boiling water bath for 3 minutes before loading (H). Lanes 1,2 – M-OmpA U, H; lanes 3,4 – I-OmpA U, H; lanes 5,6 – S163G U, H; lanes 7,8 – S167G U, H; lanes 9,10 – S163G:S167G U, H.