Changes in membrane proteins of Escherichia coli K12 mediated by bacteriophage IKe-specific plasmids.

At least 3 minor proteins have been detected by sodium dodecyl sulfate polyacrylamide gel electrophoresis in the unseparated (31 000 daltons) and inner membranes (53 000 and 86 000 daltons) of a non-piliated strain of E. coli K12 bearing the phage IKe-specific resistance plasmid RM98 (Tra+); these proteins are lacking in its Tra- derivative and in the plasmidless host. In contrast, in another K12 host carrying each of different IKe-specific colicinogenic factors, an extra 30 000 dalton protein is observed in the outer membranes; a number of minor proteins seen in the inner membranes appear to be different from those observed in the RM98+ strain. The evidence suggests that the 30 000-31 000 dalton protein is transfer function specific.