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J Biol Chem, Vol. 273, Issue 29, 18109-18116, July 17, 1998
From the Biomedical Research Centre and ICRF Molecular Pharmacology
Unit, Ninewells Hospital and Medical School,
Dundee DD1 9SY, United Kingdom
Bm3R1 is a helix-turn-helix transcriptional
repressor from Bacillus megaterium whose binding to DNA is
inhibited by fatty acids and a wide range of compounds that modulate
lipid metabolism. The inactivation of Bm3R1/DNA binding activity
results in the activation of transcription of the operon encoding a
fatty acid hydroxylase, cytochrome P450 102. The metabolic role of this
operon is unknown. It is possible that it is involved in the synthesis of modified fatty acids as part of normal cellular metabolism or may
represent a protective mechanism by which B. megaterium detoxifies harmful foreign lipids. In this report we demonstrate that
polyunsaturated fatty acids (PUFA) activate the transcription of the
CYP102 operon. These PUFA are the most potent activators of the CYP102
operon observed to date, and we show that their effects are due to
binding directly to Bm3R1. In addition, cultures that have been treated
with the CYP102 inducer, nafenopin, are protected against PUFA
toxicity. Resistance to PUFA toxicity is also seen in a Bm3R1-deficient
strain that constitutively expresses CYP102. The resistant phenotype of
this Bm3R1 mutant strain is reversed by specific chemical inactivation
of CYP102. These data demonstrate that Bm3R1 can act as a direct sensor
of toxic fatty acids and, in addition, provide the first direct
evidence of fatty acids binding to a prokaryotic transcription factor.
The Repressor Protein, Bm3R1, Mediates an Adaptive Response
to Toxic Fatty Acids in Bacillus megaterium
Copyright © 1998 by The American Society for Biochemistry and Molecular Biology, Inc.
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