JAC Advance Access published online on May 18, 2004
Journal of Antimicrobial Chemotherapy, doi:10.1093/jac/dkh241
© 2004 by The British Society for Antimicrobial Chemotherapy
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1 Mycobacterium Biology Laboratory, Institute of Molecular
and Cell Biology, 30 Medical Drive,
Singapore 117609, Republic of Singapore
* To whom correspondence should be addressed. E-mail: sinhai{at}imcb.nus.edu.sg.
Objectives: To determine whether the
fatty acid synthesis enzyme malonyl coenzyme A:acyl carrier protein transacylase
(MCAT) is involved in the growth-inhibitory effect of trifluoperazine
in the tubercle bacillus Mycobacterium bovis BCG. Methods: BCG was grown in liquid culture with
various concentrations of trifluoperazine and growth was monitored
by OD measurement. To determine the effect of trifluoperazine on
MCAT protein level, total protein was extracted from BCG cultures
and was analysed by 2D gel electrophoresis and western blot. To confirm
trifluoperazine-dependent reduction in the MCAT protein level, two
BCG strains overexpressing MCAT at a low and high constitutive level
were similarly tested. The synergic effect of trifluoperazine and isoniazid
was tested at sub-MIC levels in liquid cultures. Results: Trifluoperazine inhibition of growth
correlates with reduction in the steady-state level of MCAT protein.
Overexpression of MCAT confers resistance to trifluoperazine. Trifluoperazine
acts synergically (albeit weakly) with isoniazid and no resistance
towards isoniazid alone was observed due to overexpression of MCAT.
This suggests MCAT to be a specific target of trifluoperazine. Conclusion: These results indicate MCAT as a
target of trifluoperazine and provide an explanation for the inhibitory
effect of trifluoperazine on mycobacterial lipid synthesis observed
earlier. This makes MCAT a potential target for new antimycobacterials.
Revised March 8, 2004
Accepted March 18, 2004
Brief report
Role for malonyl coenzyme A:acyl carrier protein
transacylase (MCAT) in the growth-inhibitory effect of the calmodulin
antagonist trifluoperazine in Mycobacterium bovis BCG
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