NUCLEOTIDE SYNTHESIS AND METABOLISM IN MYCOBACTERIA

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DESCRIPTION (Adapted from the Applicant's Abstract): Many of the mycobacterial cell wall polymers are derived from basic building blocks of nucleoside diphosphate-sugar residues such as GDP-mannose and UDP-galactose which require nucleoside triphosphates (NTPs) such as GTP or UTP for each molecule of the sugar residue present in the polymer. Nothing is known about how the precursor NTP pool in the mycobacterial cells is regulated. The Investigator has recently isolated 4 different proteins from Mycobacterium smegmatis that modulate the specificity of nucleoside diphosphate kinase (Ndk) to primarily synthesize either GTP, or UTP, or CTP. Whether such proteins may play a role in supplying specific NTPs for cell wall/envelope components is not know at present. The investigators propose to characterize Ndk-complexing proteins in M. bovis-BCG, isolate their genes, and attempt to make knockout mutations to examine if loss of the gene functions may result in altered cell wall synthesis as characterized chemically. They have also recently reported the secretability of two ATP-utilizing enzymes (Ndk and ATPase) of M. bovis BCG. The secretion of these two enzymes is facilitated in the presence of eukaryotic proteins such as bovine serum albumin or ovalbumin. Preliminary evidence suggests that the presence of receptors on the surface of M. bovis BCG cells that bind ovalbumin. They propose to isolate and characterize these receptors. Additionally, they would like to make deletion and site-directed mutations in the ndk gene of M. bovis BCG to examine the role of putative sequences (motifs) in the secretability of Ndk.