Roles of Glucitol in the GutR-mediated Transcription Activation
Process in Bacillus subtilis
GLUCITOL INDUCES GutR TO CHANGE ITS CONFORMATION AND TO BIND
ATP*
Karen K. H.
Poon
,
Joyce C.-L.
Chu, and
Sui-Lam
Wong§
From the Division of Cellular, Molecular and Microbial Biology,
Department of Biological Sciences, University of Calgary, Calgary,
Alberta T2N 1N4, Canada
GutR is a 95-kDa glucitol-dependent
transcription activator that mediates the expression of the
Bacillus subtilis glucitol operon. Glucitol allows GutR to
bind tightly to its binding site located upstream of the
gut promoter. In this study, a second functional role of
glucitol is identified. Glucitol induces GutR to change its
conformation and triggers GutR to bind ATP efficiently. After
sequential binding of glucitol and ATP to GutR, GutR adopts a new
conformation by forming a compact structure that is resistant to
trypsin digestion. Under this condition, the ATP·glucitiol·GutR complex can dissociate slowly from the gutR-binding site
(t1/2 = 274 min). Interestingly, if ATP in the
ATP·glucitiol·GutR complex is replaced by ADP, GutR adopts another
conformation and can dissociate from the gutR-binding site
even faster (t1/2 = 82 min). In all these GutR-DNA
binding studies in the presence of different ligands (glucitol, ATP, or
ADP), only the off-rate is affected. The vital role of ATP in the
GutR-mediated transcription activation process is reflected by the poor
transcription from the gut promoter with GutR(D285A) which
has a mutation in the motif B of the putative ATP-binding site. A
working model for this transcription activation process is presented.
*
This work was supported in part by a research grant from the
Natural Sciences and Engineering Research Council (NSERC) of Canada (to
S. L. W.).The costs of publication of this
article were defrayed in part by the
payment of page charges. The article must therefore be hereby marked
"advertisement" in
accordance with 18 U.S.C. Section
1734 solely to indicate this fact.
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