Truncation of the C-terminal domain from CgtA of Mycobacterium smegmatis reduces its ribosome binding property but increases its GTPase activity

Tuberculosis (TB), caused by Mycobacterium tuberculosis , presents a significant public health concern due to the emergence and prevalence of multi-drug-resistant strains. On this note, this study explores the potential of CgtA as a therapeutic drug target, derived from the bacterium Mycobacterium smegmatis , a well-established model organism used globally for TB research. CgtA is a GTPase protein essential for the survival of many bacterial species, and is involved in several essential processes; although the exact pathways of its association with these processes are still unknown. CgtA exhibits a three-domain structure, comprising of the conserved Obg and GTPase domain, followed by a highly variable C-Terminal Domain (CTD) of unknown function. This study explores the interaction and activity of CgtA from M. smegmatis (CgtA ms ) with ribosome. Through comparative ribosome binding analyses and Surface Plasmon Resonance studies, we demonstrate that the CTD of CgtA ms facilitates binding of CgtA ms to both 70S ribosomes and 50S ribosomal subunits. Interestingly, the 50S ribosome-associated GTPase activity of wt CgtA ms increased by 2.6-fold, while that of CTD-truncated CgtA ms increased by 3.5-fold., suggesting CTD acts as a negative regulator of ribosome-associated GTPase activity of CgtA ms . These observations suggest that the CTD-CgtA ms have a dual role; as a positive factor for ribosome binding, and as a negative factor for GTPase activity. Given the high amino acid sequence similarity between CgtA from M. smegmatis and M. tuberculosis , these findings may facilitate the investigation of CgtA as a potential therapeutic target for TB. • The CTD of Mycobacterium smegmatis CgtA i.e., CgtA ms is associated with the binding of CgtA ms to both 70S and 50S ribosomes. • The OCT-like fold of the CTD of CgtA ms might play a significant role for ribosome binding. • The CTD of CgtA ms acts as a negative regulator of the ribosome-associated GTPase activity of CgtA ms . • The CTD of CgtA ms has a dual role; as a positive factor for ribosome binding and a negative factor for GTPase activity. • Because of the close sequence similarity between CgtA ms and CgtA of M. tuberculosis , these findings will help TB research.