Coenzyme A biosynthesis pathway
proteins are potential targets for developing inhibitors against bacteria including Mycobacterium tuberculosis. We have evaluated two
enzymes in this pathway:
phosphopantetheine adenylyltransferase (
CoaD) and
dephospho CoA kinase (CoaE) for essentiality and selectivity. Based on the previous transposon mutagenesis studies,
coaD had been predicted to be a non-essential gene in M.
tuberculosis. Our bioinformatics analysis showed that there is no other functional homolog of this
enzyme in M.
tuberculosis, which suggests that
coaD should be an essential gene. In order to get an unambiguous answer on the essentiality of
coaD, we attempted inactivation of
coaD in wild type and merodiploid backgrounds. It was found that
coaD could only be inactivated in the presence of an additional gene copy, confirming it to be an essential gene. Using a similar approach we found that CoaE was also essential for the survival of M.
tuberculosis. RT-PCR analysis showed that both
coaD and coaE were transcribed in M.
tuberculosis.
Amino acids alignment and phylogenetic analysis showed
CoaD to be distantly related to the human counterpart while CoaE was found to be relatively similar to the human
enzyme. Analysis of
CoaD and CoaE structures at molecular level allowed us to identify unique residues in the Mtb
proteins, thus providing a selectivity handle. The essentiality and selectivity analysis combined with the published biochemical characterization of
CoaD and CoaE makes them suitable targets for developing inhibitors against M.
tuberculosis.