Vol. 273, Issue 4, 2435-2444, January 23, 1998
Truncation of MalF Results in Lactose Transport via the Maltose
Transport System of Escherichia coli
Gonzalo
Merino and
Howard A.
Shuman
From the Department of Microbiology, College of Physicians and
Surgeons, Columbia University, New York, New York 10032
The active accumulation of maltose and
maltodextrins by Escherichia coli is dependent on the
maltose transport system. Several lines of evidence suggest that the
substrate specificity of the system is not only determined by the
periplasmic maltose-binding protein but that a further level of
substrate specificity is contributed by the inner membrane integral
membrane components of the system, MalF and MalG.
We have isolated and characterized an altered substrate specificity
mutant that transports lactose. The mutation responsible for the
altered substrate specificity results in an amber stop codon at
position 99 of MalF. The mutant requires functional MalK-ATPase activity and hydrolyzes ATP constitutively. It also requires MalG. The
data suggest that in this mutant the MalG protein is capable of forming
a low affinity transport path for substrate.
Copyright © 1998 by The American Society for Biochemistry and Molecular Biology, Inc.