Preliminary Crystallographic Resarch Of AimR Protein In Phage Communication System

Quorum sensing is a common phenomenon in bacteria that allows them to produce signaling molecules that participate in cell-cell communication,thereby synchronizing their behavior according to population density.The phenomenon of quorum sensing also exists in phages.When the host population density changes,the temperate phages selectively enter the lysis pathway to lyse the cells,or enter the lysogenic pathway to protect the cells from infection.Either way,phage proliferation is guaranteed.The newly discovered arbitrium communication system enriches the quorumsensing phenomenon among phages.As a key protein in the system,AimR protein mediates the transformation of phage lysis-lysogeny cycle by binding to signal peptides or targeted DNA.Among them,the participation of signal peptide plays an important role in the cycle conversion.Its binding with AimR receptor protein directly leads phage to enter the lysogenic cycle,which ensures the phage reproduction in the later period.At present,the molecular mechanism of the function of the whole system is not clear,so it is particularly important to understand the structural basis of recognition between signal peptide and AimR receptor protein.We expressed AimR full-length protein in E.coli cells and found that its binding with SAIRGA peptide would cause changes in aggregation state.When AimR binds to the peptide,it exists in the form of dimer,while when AimR is not bound to the peptide,it exists in the form of higher aggregation.And SAIRGA peptide was found to be a necessary condition for protein crystallization,it was speculated that the binding of protein and its specific signal peptide was the key to its function.There are many flexible regions in AimR protein.Through protease cutting experiment and protein secondary structure prediction,the flexible region is located at the N-terminal of the protein.Two truncated body proteins with the flexible region removed were designed,it was found that the aggregation state of the two truncated body proteins changed in the solution and both existed in the form of tetramers,indicating that the flexible region of the N-terminal had a significant influence on the oligomerization of proteins,which may further affect the function of AimR protein.In the crystallization experiment,it was found that Benzidine and Mg²⁺play an important role in protein crystallization.It was suggested that they could be incubated with proteins in the purification process,and it was found that they could significantly improve the state of crystal accumulation.The obtained selenoproteins also exist as dimers in solution after binding to the peptide,and SAIRGA peptide is also a necessary condition for the crystallization of selenoproteins.After optimization,the crystal diffraction rate of selenoprotein has reached 3.4（?）,reaching the resolution of phase resolution.Meanwhile,the crystal optimization of Native protein is still continuing.This study provides reference for the analysis of the structure of AimR protein and elucidation of the molecular mechanism of AimR-mediated phage communication system,and provides ideas for the use of phages to control bacterial flora and the treatment of viral diseases.