Affiliation:
1. Department of Biology and Chemistry, University of Osnabrück, D-49069 Osnabrück, Germany
Abstract
ABSTRACT
The membrane-bound protein EIICB
Glc
encoded by the
ptsG
gene is the major glucose transporter in
Escherichia coli
. This protein is part of the phosphoenolpyruvate:glucose-phosphotransferase system, a very important transport and signal transduction system in bacteria. The regulation of
ptsG
expression is very complex. Among others, two major regulators, the repressor Mlc and the cyclic AMP-cyclic AMP receptor protein activator complex, have been identified. Here we report identification of a novel protein, YeeI, that is involved in the regulation of
ptsG
by interacting with Mlc. Mutants with reduced activity of the glucose-phosphotransferase system were isolated by transposon mutagenesis. One class of mutations was located in the open reading frame
yeeI
at 44.1 min on the
E. coli
K-12 chromosome. The
yeeI
mutants exhibited increased generation times during growth on glucose, reduced transport of methyl-α-
d
-glucopyranoside, a substrate of EIICB
Glc
, reduced induction of a
ptsG-lacZ
operon fusion, and reduced catabolite repression in lactose/glucose diauxic growth experiments. These observations were the result of decreased
ptsG
expression and a decrease in the amount of EIICB
Glc
. In contrast, overexpression of
yeeI
resulted in higher expression of
ptsG
, of a
ptsG-lacZ
operon fusion, and of the autoregulated
dgsA
gene. The effect of a
yeeI
mutation could be suppressed by introducing a
dgsA
deletion, implying that the two proteins belong to the same signal transduction pathway and that Mlc is epistatic to YeeI. By measuring the surface plasmon resonance, we found that YeeI (proposed gene designation,
mtfA
) directly interacts with Mlc with high affinity.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology