title: Regulated proteolysis controls mucoid conversion in Pseudomonas aeruginosa.
abstract: Overproduction of the exopolysaccharide alginate causes mucoid conversion in Pseudomonas aeruginosa and is a poor prognosticator in cystic fibrosis. The ECF sigma factor AlgU and its cognate anti-sigma factor MucA are two principal regulators of alginate production. Here, we report the identification of three positive regulators of alginate biosynthesis: PA4033 (designated mucE), PA3649 (designated mucP), and algW. MucE, a small protein (9.5 kDa), was identified as part of a global mariner transposon screen for new regulators of alginate production. A transposon located in its promoter caused the overexpression of MucE and mucoid conversion in P. aeruginosa strains PAO1 and PA14. Accumulation of MucE in the envelope resulted in increased AlgU activity and reduced MucA levels. Three critical amino acid residues at the C terminus of MucE (WVF) were required for mucoid conversion via two predicted proteases AlgW (DegS) and MucP (RseP/YaeL). Moreover, as in Escherichia coli, the PDZ domain of AlgW was required for signal transduction. These results suggest that AlgU is regulated similarly to E. coli sigma(E) except that the amino acid triad signals from MucE and other envelope proteins that activate AlgW are slightly different from those activating DegS.
authors.affiliation: Department of Biochemistry and Microbiology, Joan C. Edwards School of Medicine, Marshall University, Huntington, WV 25755-9320, USA.
authors.forename: Dongru
authors.initials: D
authors.lastname: Qiu
authors.forename: Vonya M
authors.initials: VM
authors.lastname: Eisinger
authors.forename: Donald W
authors.initials: DW
authors.lastname: Rowen
authors.forename: Hongwei D
authors.initials: HD
authors.lastname: Yu
mesh_terms: D000464:Alginates; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology; D004251:DNA Transposable Elements; D020723:Glucuronic Acid / Q000096:biosynthesis; D006025:Glycosaminoglycans / Q000378:metabolism*; D006603:Hexuronic Acids; D011550:Pseudomonas aeruginosa / Q000378:metabolism*; D012097:Repressor Proteins / Q000737:chemistry / Q000502:physiology; D012697:Serine Endopeptidases / Q000502:physiology; D012808:Sigma Factor / Q000502:physiology
chemical_list: C079619:AlgU protein, Pseudomonas aeruginosa; C097646:AlgW protein, Pseudomonas aeruginosa; D000464:Alginates; D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D006025:Glycosaminoglycans; D006603:Hexuronic Acids; C107895:MucA protein, Pseudomonas; D012097:Repressor Proteins; D012808:Sigma Factor; C046129:mucoid exopolysaccharide (P aeruginosa); D020723:Glucuronic Acid; C097649:MucD protein, Pseudomonas aeruginosa; D012697:Serine Endopeptidases