Exploring the structural and dynamical features of bacterial-tubulin FtsZ

FtsZ, a bacterial tubulin, plays a crucial role in the cytokinesis process. It shares structural similarities with tubulin, as it consists of two domains-N-terminal and C-terminal domains. The protein assembles to form single-stranded protofilaments that exhibit a dynamic phenomenon known as treadmilling where the FtsZ filaments appear to execute a unidirectional movement even though individual monomers constituting the filament do not move. Despite forming protofilaments, an FtsZ molecule requires a conformational switch to form stable contacts with neighboring subunits in a filament. Therefore, FtsZ has two well-characterized conformations based on its polymerization propensity: 1) R state, preferred by the monomeric FtsZ and 2) T state, preferred by the polymeric FtsZ. The treadmilling ability of FtsZ is coupled with the conformational switch and the GTPase activity of the protein as hydrolysis-deficient mutants of FtsZ do not treadmill. We employ all-atom molecular dynamics simulations to investigate certain structural and dynamical features of the protofilaments by considering FtsZ heptamers as our model system. We simulated FtsZ filaments in three nucleotide states-GTP, GDP, and GDP-Pi-to understand the conformational states of the terminal monomers, interface dynamics of the filaments, and important interactions at the protein interdomain and interface regions. Our study reveals that the γ-phosphate binding loop T3 prompts the structural rearrangements at the interface post hydrolysis.