Structural Basis Of The Type 1 Pili Biogenesis In Bacteria

Objective:In this study we use X-ray diffraction crystallography to determine the 3-D structure of the pathogenic factors and their biosynthetic pathway related protein.According to the structure,we explain the molecular mechanisms of the type 1 pili biogenesis and design peptide anti-infective drug.Method:Through the expression of recombinant proteins,the bacterial express system BL21(DE3),obtained type 1 pili secretion system protein.And we use the trypsin digest the protein,then crystallize the Membrane protein complex.Using X-ray diffraction technology tests of the proceeds of the crystal diffraction ability.Collect the diffraction image by Shanghai Synchrotron Radiation Facility.Process the diffraction image data to determine and refine the 3D-structure of type 1 pili secretion system protein.Result:We have obtained the homogeneous and pure protein sample of type 1 pili secretion system.The crystal of FimD-FimCFGH protein could diffract to 3.5-4 angstrom.We determined the 3D-structure of type 1 pili secretion system protein.Conclusion:From the structure and the preliminary biochemical analysis show that It is not need for energy transfer process in Gram negative bacteria outer membrane.Pili subunits are assembled by FimD and FimC proteins.FimF-FimG-FimH sub-complex is insert the FimD protein usher domain.The N-terminal of each pili subunit about ten amino acids can insert the next pili subunit and make it more stable.Comformational change provides energy for the secretion of fimbriae.Structure of the FimD-FGCH protein has switched from a high-energy state to a low energy state.