Phenothiazines have been reported for anti-mycobacterial activity by inhibiting
calcium binding proteins,
potassium transport processes of phagolysosomes,
NADH dependent oxygen consumption by M.
tuberculosis membranes and
DNA, and
lipid synthesis of the bacterium.
Thioridazine (TZ), chloropromazine (CPZ) and
trifluoperazine (TFP) belong to the class of
phenothiazines widely used as
neuroleptic drugs.
Trifluoperazine, a
calmodulin antagonist in eukaryotes, binds to a similar
protein containing prototypical EF hand to bind to
calcium in M.
tuberculosis.
Calmodulin, a
calcium binding protein, plays a critical role in regulating the activities of several
enzymes in response to intracellular
calcium levels. Since calmodulins are best characterized in eukaryotes as opposed to prokaryotes, the presence of
calmodulin-like activity in M.
tuberculosis, the causative agent of
tuberculosis, is unknown. We have provided biochemical evidence that M.
tuberculosis recombinant (r) Rv1211 gene product stimulates the activities of heterologous
calcium-deficient
NAD-kinase and bovine brain
phosphodiesterase (PDE), much like the eukaryotic calmodulins. Further we have shown that
EGTA, a
calcium chelator, inhibits rRv1211-stimulated
NAD-kinase and PDE activities. We have also shown that
trifluoperazine interferes with the activation of
NAD-kinase and PDE activities by Rv1211. Using a bioinformatics approach, we have shown that Rv1211 contains one prototypical
calcium-binding EF-hand motif, a characteristic feature of calmodulins. Based on these data, we conclude that Rv1211 encodes a
protein with
calmodulin-like activity (CAMLP) in the human pathogen M.
tuberculosis and acts as a potential target for
trifluoperazine.