Regulatory Mechanism Of Gatekeeper SepD On Two Secretory Signaling Pathways Of T3SS Effectors

Many Gram-negative pathogens and Gram-positive pathogens have unique effector protein exportation mechanisms.Eight secretory systems have been identified,named T1SS-T8SS.Type 3 secreted effector proteins are very important virulence factors produced by many Gram-negative pathogens.The bacterial type 3 secretion system is a multi-protein complex composed of about 20 proteins,which resembles a syringe and extended across bacterial double-membranes,which has a common origin with the flagellum device.Bacteria can use T3SS to directly inject effector proteins into the cytoplasm of the host cell,thereby regulating host cell function and signal transduction pathway,destroying the host defense,promoting bacterial proliferation,and leading to disease.Since the concept of a type 3 secretion system was proposed,the study of related molecular mechanisms has furthered our understanding of it.In contrast to the signal peptides in other secretory machineries,there is no conserved signal sequence when the protein is secreted or transported through the bacterial type 3 secretion system.A variety of secretory signals that guide the secretion of type 3 secreted protein have been discovered in the recent study.Thesis introduces the categories of bacterial type 3 secretion system,the types of secreted proteins in the secretory system and is focused on molecular characters of secretion signals.We using GST PULL DOWN,protein secretion and other experimental methods,it was found that the four typical effector proteins of EHEC were located in their NSS region,and the secretory signaling molecules were composed of amino acid sequences.We also found that the switch protein SepD can bind to the chaperone protein CesT to control the orderly output of effectors.We hope to provide new ideas for the development of new antibacterial drugs.