Era, a GTPase-like protein of the Ras family, does not control ribosome assembly in Mycobacterium tuberculosis

Era GTPase is universally present in microbes including Mycobacterium tuberculosis (Mtb) complex bacteria. While Era is known to regulate ribosomal assembly in Escherichia coli and predicted to be essential for in vitro growth, its function in mycobacteria remains obscured. Herein, we show that Era ortholog in the attenuated Mtb H37Ra strain, MRA_2388 (annotated as Era(MT)) is a cell envelope localized protein harbouring critical GTP-binding domains, which interacts with several envelope proteins of Mtb. The purified Era from M. smegmatis (annotated as Era(MS)) exhibiting similar to 90% sequence similarity with Era(MT), exists in monomeric conformation. While it is co-purified with RNA upon overexpression in E. coli, the presence of RNA does not modulate the GTPase activity of the Era(MS) as against its counterpart from other organisms. CRISPRi silencing of era(MT) does not show any substantial effect on the in vitro growth of Mtb H37Ra, which suggests a redundant function of Era in mycobacteria. Notably, no effect on ribosome assembly, protein synthesis or bacterial susceptibility to protein synthesis inhibitors was observed upon depletion of Era(MT) in Mtb H37Ra, further indicating a divergent role of Era GTPase in mycobacteria.