Studies on the structural evolution of Tobamovirus and GTPase Obg CgtA

Chatterjee, Ananya (2026) Studies on the structural evolution of Tobamovirus and GTPase Obg CgtA. PhD thesis, Indian Institute of Science Education and Research Kolkata.

Text (Phd thesis of Ananya Chatterjee (17RS001)) 17RS001.pdf - Submitted Version Restricted to Repository staff only Download (7MB)

Abstract

Structural biology offers a critical investigative framework for linking molecular architecture with biological function, which is essential for mapping adaptation and tracing evolutionary trajectories. This research deployed a unified, multi-scale approach across microbial systems, integrating Cryo-Electron Microscopy (cryo-EM), bioinformatics, and phylogenetics to explore molecular integrity under environmental and evolutionary pressures. The structural investigation utilized high-resolution cryo-EM to reconstruct the 3D structures of two Tobamoviruses, Cucumber Green Mottle Mosaic Virus (CGMMV) and Tomato Mottle Mosaic Virus (ToMMV), at 2.86 & 2.71 Å resolution, respectively. This atomic-level visualization of the capsid protein subunits provided key insights into markers for the characteristic thermostability of Tobamoviruses. Comparative analysis of the same revealed the direct correlation of protein sequence with host variability & specificity. Extending the analysis to the evolutionary scale, the study investigated the bacterial protein, GTPase Obg/CgtA, focusing on the variability of its C-Terminal Domain (CTD). Bioinformatic and phylogenetic techniques quantified sequence variability across diverse bacterial species, identifying distinct patterns of conservation and divergence within the CgtA-CTD. These patterns were successfully correlated with bacterial membrane properties and overall phylogenetic diversity. The study further traced the retention and genetic transfer of Obg into eukaryotic systems. Collectively, this work provides a robust framework for investigating molecular integrity using structural biology and establishes structural biology as an efficient tool to study evolutionary biology, equipped with cutting-edge techniques like cryo-EM and bioinformatics.

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