title: Regulatory role of PopN and its interacting partners in type III secretion of Pseudomonas aeruginosa.
abstract: The type III secretion system (T3SS) of Pseudomonas aeruginosa plays a significant role in pathogenesis. We have previously identified type III secretion factor (TSF), which is required for effective secretion of the type III effector molecules, in addition to the low calcium signal. TSF includes many low-affinity high-capacity calcium binding proteins, such as serum albumin and casein. A search for the TSF binding targets on the bacterial outer membrane resulted in identification of PopN, a component of the T3SS that is readily detectable on the bacterial cell surface. PopN specifically interacts with Pcr1, and both popN and pcr1 mutants have a constitutive type III secretion phenotype, suggesting that the two proteins form a complex that functions as a T3SS repressor. Further analysis of the popN operon genes resulted in identification of protein-protein interactions between Pcr1 and Pcr4 and between Pcr4 and Pcr3, as well as between PopN and Pcr2 in the presence of PscB. Unlike popN and pcr1 mutants, pcr3 and pcr4 mutants are totally defective in type III secretion, while a pcr2 mutant exhibits reduced type III secretion. Interestingly, PopN, Pcr1, Pcr2, and Pcr4 are all secreted in a type III secretion machinery-dependent manner, while Pcr3 is not. These findings imply that these components have important regulatory roles in controlling type III secretion.
authors.affiliation: Department of Molecular Genetics and Microbiology, P.O. Box 100266, University of Florida, Gainesville, FL 32610-0266, USA.
authors.forename: Hongjing
authors.initials: H
authors.lastname: Yang
authors.forename: Zhiying
authors.initials: Z
authors.lastname: Shan
authors.forename: Jaewha
authors.initials: J
authors.lastname: Kim
authors.forename: Weihui
authors.initials: W
authors.lastname: Wu
authors.forename: Wei
authors.initials: W
authors.lastname: Lian
authors.forename: Lin
authors.initials: L
authors.lastname: Zeng
authors.forename: Laijun
authors.initials: L
authors.lastname: Xing
authors.forename: Shouguang
authors.initials: S
authors.lastname: Jin
mesh_terms: D036002:ADP Ribose Transferases / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics*; D001427:Bacterial Toxins / Q000235:genetics; D002135:Calcium-Binding Proteins / Q000235:genetics*; D004252:DNA Mutational Analysis; D004797:Enzyme-Linked Immunosorbent Assay; D006367:HeLa Cells; D006801:Humans; D016296:Mutagenesis; D010957:Plasmids; D011550:Pseudomonas aeruginosa / Q000235:genetics / Q000472:pathogenicity*
chemical_list: D001426:Bacterial Proteins; D001427:Bacterial Toxins; D002135:Calcium-Binding Proteins; D036002:ADP Ribose Transferases; C444820:exoenzyme S