Impact of Fe + 2 ions on structural integrity of A0A6P1CI42_RHITR NifA protein from Rhizobium tropici strain CIAT 899

A0A6P1CI42_RHITR, a protein originating from Rhizobium tropici strain CIAT 899, has emerged as a key player in leguminous plant symbiosis and nitrogen fixation processes. Understanding the intricate details of its structure and function holds immense significance for unraveling the molecular mechanisms underlying its biological activities. In this study, we employed molecular modeling and molecular dynamics (MD) simulations to investigate the A0A6P1CI42_RHITR protein, with a specific emphasis on the influence of Fe-atoms, linker structural integrity, and conformational changes within the GAF domain. Our findings unveiled noteworthy conformational changes in the A0A6P1CI42_RHITR protein, particularly within the GAF domain, when Fe-atoms were present compared to its apo form. Significant conformational rearrangements after an initial 20 ns, accompanied by the opening of the ligand substrate accommodating loop in the GAF domain influenced by Fe-atoms was observed. At the residue level, the investigation revealed substantial activity variations in individual residues, particularly in those contributing to the GAF domain from positions 51 to 223. Intriguingly, the presence of Fe-atoms led to controlled movement of conserved cysteine residues at positions 467 and 472, indicating a correlation between interlinker domain motion and the activity of the GAF domain loop responsible for substrate accommodation. Moreover, in the presence of Fe-atoms, the distance between Cys467 and Cys472 residues was maintained, ensuring the overall structural integrity of the interdomain loop necessary for protein activation. Conversely, in the apo form, a sudden flip motion of cysteine residues' thiol groups was observed, leading to a loss of structural integration. Overall, our study utilizing molecular modeling and MD simulations offers valuable insights into the structural dynamics and functional implications of the A0A6P1CI42_RHITR protein.Communicated by Ramaswamy H. Sarma.