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J. Bacteriol., 09 1995, 5261-5269, Vol 177, No. 18
D Mayer, V Schlensog and A Bock
The gene budR, whose product is responsible for induction of the butanediol
formation pathway under fermentative growth conditions in Klebsiella
terrigena, has been cloned and sequenced. This gene is separated from the
budABC operon by a nontranslated region of 106 bp and transcribed in the
opposite direction. budR codes for a protein of molecular weight 32,124,
the sequence of which exhibits characteristics of regulators belonging to
the LysR family. When transferred into the heterologous host Escherichia
coli, budR activates expression of budA'- lacZ transcriptional and
translational fusions with a regulatory pattern identical to that in K.
terrigena, namely, induction by acetate, low pH, and anaerobiosis.
Induction by acetate was specific, indicating that it is the physiological
inducer. Primer extension analysis located the start site of transcription
to two positions, 23 and 24 bp upstream of the budR initiation codon, and
also showed that BudR strongly autoregulates its own expression. The
products of fhlA, arcA, hip, ntrA, and katF did not influence expression of
the bud operon. A mutation in fnr, however, led to a threefold increase in
expression, indicating that Fnr acts as a repressor. The results support
the notion that BudR coordinates the activity of the energy- conserving,
nonreductive, but acidifying acetate formation pathway with the expression
of the non-energy-conserving, reductive, but nonacidifying butanediol
pathway.
Copyright © 1995, American Society for Microbiology
Identification of the transcriptional activator controlling the butanediol fermentation pathway in Klebsiella terrigena
Lehrstuhl fur Mikrobiologie, Universitat Munchen, Germany.
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