The porin protein of the outer membrane of Escherichia coli: reactivity in immunoblotting, antibody-binding by the native protein, and cross-reactivity with other enteric bacteria.

The experimental conditions for antibody-binding by the 38.5 kD porin protein of an E. coli 055 strain in immunoblotting were investigated. A non-ionic detergent in the buffer which contained the primary antibody was required for antibody-binding by electroblots of the SDS-denatured protein. Immunoblotting, using antiserum absorbed with bacteria or the outer membrane (OM) of the E. coli 055 strain, showed results concordant with inaccessibility to antibodies of the 38.5 kD porin protein in its native configuration in the bacterial cells, but immunoreactivity when contained in the OM. OM from strains of different genera of the Enterobacteriaceae and antisera against these strains when used in immunoblot analyses showed that the E. coli 055 porin protein harboured antigenic determinants which are common to the various genera of the enteric bacilli. Cross-reactivity with non-enteric Gram-negative bacteria was not observed.