Studies on the Mechanisms of Action of a Bacterial Essential Obg-GTPase Protein CgtA

Chatterjee, Ananya (2016) Studies on the Mechanisms of Action of a Bacterial Essential Obg-GTPase Protein CgtA. PhD thesis, Indian Institute of Science Education and Research Kolkata.

PDF (PhD thesis of Ananya Chatterjee (09RS046)) Ananya_Chatterjee_DBS_PPD_IISERK_DEC_2016-compressed.pdf - Submitted Version Restricted to Repository staff only Download (7MB)

Abstract

CgtA is a highly conserved, essential and multifunctional bacterial protein that is being considered as a potential drug target. Due to its importance extensive studies are needed to understand its mode of action, how the three individual domains of CgtA work during cellular activity. In this present study, some of the mechanisms of action of the CgtA protein were deciphered from V. cholera N16961. First chapter in this thesis reports about, the effect of point mutations in two conserved residue; (Gly98Asp) in Obg domain which causes reduction of the GTPase activity of CgtAvc, that could be partially restored by a second mutation (Try194Gly) in the switch I region of the GTPase domain. The results suggests that the two domains of the CgtAvc i.e., Obg domain and the GTPase domain cross-talk among themselves and the signal gets transmitted from Obg domain to GTPase domain or vice versa. The biochemical phenomena were further investigated by using MD simulation tools in the second chapter. MD simulations studies revealed that the Obg domain undergoes both angular and rotational movement with respect to the GTPase domain upon GTP binding and GTP hydrolysis (GDP bound state) due to the change in phi psi angle of the residues Leu161-Leu164, located in the connector of Obg domain and GTPase domain. The salt bridge formation in the inter-domain space between Asp98 and Arg242 in CgtAvc(Gly98Asp) mutant restricts both the magnitude and the direction of movement of the Obg domain. Therefore, suggesting that the two domains need to cross-talk among themselves by the inter-domain movement. The third chapter depicts the function of three glycine rich loops of the Obg domain; that are mainly involved in the binding of the CgtA protein with the ribosome. Whereas the role of Cterminal domain still remains a mystery to be solved. In the last part of this thesis, the growth and morphological changes of the V. cholerae cells upon nutritional stress were observed and also the expression level of the cgtA mRNA was measured that show a transient increase of cgtA expression at the mRNA level immediately upon nutritional shift.

Actions (login required)

View Item