Active Transport of Maltose in Escherichia coli K12

A “periplasmic” maltose binding protein was purified from Escherichia coli. This protein is shown to be under the same positive control as the whole maltose system, and its synthesis is inducible by maltose. This binding protein is coded by malE, one of the three cistrons of the malB region involved in the transport of maltose. The binding characteristics of this protein, as well as the kinetics of release of bound maltose, suggest that the binding protein can exist in two states differing by their affinity towards maltose. The significance of this result is discussed in view of the role that the protein is believed to play in maltose transport.