부산대학교 도서관

The auto-inducer-mediated virulence gene expression and biofilm formation in Vibrio sp. uses a highly evolved two-component phosphotransfer system, involving a histidine sensor kinase (LuxQ), an Hpt domain protein (LuxU) and a universal response regulator (LuxO), to process the signal. At low and high cell density, the phosphotransfer reaction occurs differently leading to the activation or deactivation, respectively, of the global repressor which in turn regulates the virulence. Here the molecular details of signal processing and signal decay have been studied using structural modelling and molecular dynamics simulation of LuxQ, LuxU and LuxO individual proteins and protein–protein complexes with and without the phosphate group. The stability, conformational flexibility and structural changes associated with phosphotransfer of the individual protein and the protein–protein complexes are compared. The root mean square deviations and the root mean square fluctuations of the phosphorylated and unphosphorylated proteins showed significant differences in these two processes. The principal component analysis points out the remarkable differences in the essential motions of the systems, which depend not only on the phosphorylated complex but also on the key phosphorylation of the individual protein component. This observation is also highlighted by the dynamic cross-correlation matrix (DCCM) analysis where concerted motions are found to differ depending on the state of phosphorylation. Evaluation of the equilibrated structures and their free energy reveals that the reverse transfer of phosphate during signal decay is energetically less favourable.