[Interaction of the membrane transport proteins in E. coli K12]

The inhibition kinetics of NO2PheGal transport by MeGlc in E. coli K12 were studied. The inhibitory effect was observed only at definite ratio of the corresponding transport proteins -- enzyme IIglc and beta-galactoside permease. It was shown that in this case, beside the repressive effect of MeGlc on beta-galactoside transport, beta-galactosides (GalSGal) can also inhibit the rate of MeGle accumulation. The data obtained suggest that in the region of maximal inhibitory effect the conformation of both membrane proteins are changed, which leads to an increase in the activity of enzyme IIglc and its affinity for MeGlc. It was assumed that the phenomenon observed is not unique and is in general conformity with the postulate that under certain conditions many bacterial membrane proteins can come into interaction, thus changing their activity.