Requirement of heat and metabolic energy for the expression of inhibitory action of colicin K.

Escherichia coli B, induced for beta-galactoside permease, can accumulate thio-methyl-beta-galactoside in the cell even at 0 degrees D. At this temperature, cells adsorb colicin K but the adsorbed colicin does not inhibit thiomethyl-beta-galactoside uptake. Inhibition by colicin K is, however, seen at 0 degrees C after exposure of the colicin K-cell complex to a high temperature: a greater degree of inhibition occurs with increasing temperature or duration or exposure. There is a transition point at around 21 degrees C in Arrhenius plots of this colicin K activation reaction. If inhibitors of energy yielding reactions are present during the heat treatment, the inhibitory action of colicin K (as measured by thiomethyl-beta-galactoside uptake after returning the colicin K-cell complex to 0 degrees C and removal of the inhibitors) is prevented. These results indicate that adsorbed colicin K is converted into the active state only in the presence of metabolic energy and that cell surface fluidity appears to be concerned in this process.