Conformational dynamics and ribosomal interactions of Bacillus subtilis Obg in various nucleotide-bound states:...

Obg, a GTPase, binds to the premature 50S ribosomal subunit and facilitates recruitment of rproteins and rRNA processing to form the mature 50S subunit. This binding depends on nucleotide-induced conformational changes (GDP/GTP). However, the mechanism by which Obg undergoes conformational changes to associate with the premature 50S subunit is unknown. Therefore, 1000 ns molecular dynamics simulations were conducted to investigate this mechanism. Visualization of the simulated trajectory showed that in GDP and GTP-bound states, the C-domain moved towards the SwI region, while in GTP-Mg²⁺ and ppGpp-bound states, the C-domain shifted towards the N-tails. Further, positioning these conformations of Obg on the 50S subunit suggests possible mechanisms by which the GTP-Mg²⁺ bound state is responsible for recruiting rprotein, as well as the impact of the absence of Mg²⁺ in the GTP-bound state. Furthermore, the study provides insights into the conformational changes that may lead to the dissociation of the GDP-bound state from the 50S subunit and explores the potential role of the ppGpp-bound state in inhibiting 70S ribosome formation. Additionally, RMSF and community network analyses reveal how internal dynamics and intricate connections within Obg affect C-domain motion.