Unique C-Terminal Extension And Interactome Of Mycobacterium Tuberculosis Glmu Impacts It'S In Vivo Function And The Survival Of Pathogen

N-acetyl glucosamine-1-phosphate uridyltransferase (GlmU) is a bifunctional enzyme involved in the biosynthesis of Uridine diphosphate N-acetylglucosamine (UDP-GlcNAc). UDP-GlcNAc is a critical precursor for the synthesis of peptidoglycan and other cell wall components. The absence of a homolog in eukaryotes makes GlmU an attractive target for therapeutic intervention. Mycobacterium tuberculosis GlmU (GlmU(Mt)) has features, such as a C-terminal extension, that are not present in GlmU(orthologs) from other bacteria. Here, we set out to determine the uniqueness of GlmU(Mt) by performing in vivo complementation experiments using Rv Delta glmU mutant. We find that any deletion of the carboxy-terminal extension region of GlmU(Mt) abolishes its ability to complement the function of GlmU(Mt). Results show orthologs of GlmU, including its closest ortholog, from Mycobacterium smegmatis, cannot complement the function of GlmU(Mt). Furthermore, the co-expression of GlmU(Mt) domain deletion mutants with either acetyl or uridyltransferase activities failed to rescue the function. However, co-expression of GlmU(Mt) point mutants with either acetyl or uridyltransferase activities successfully restored the biological function of GlmU(Mt), likely due to the formation of heterotrimers. Based on the interactome experiments, we speculate that GlmU(Mt) participates in unique interactions essential for its in vivo function.