title: Phosphoryl Group Flow within the Pseudomonas aeruginosa Pil-Chp Chemosensory System: DIFFERENTIAL FUNCTION OF THE EIGHT PHOSPHOTRANSFERASE AND THREE RECEIVER DOMAINS.
abstract: Bacterial chemosensory signal transduction systems that regulate motility by type IV pili (T4P) can be markedly more complex than related flagellum-based chemotaxis systems. In T4P-based systems, the CheA kinase often contains numerous potential sites of phosphorylation, but the signaling mechanisms of these systems are unknown. In Pseudomonas aeruginosa, the Pil-Chp system regulates T4P-mediated twitching motility and cAMP levels, both of which play roles in pathogenesis. The Pil-Chp histidine kinase (ChpA) has eight "Xpt" domains; six are canonical histidine-containing phosphotransfer (Hpt) domains and two have a threonine (Tpt) or serine (Spt) in place of the histidine. Additionally, there are two stand-alone receiver domains (PilG and PilH) and a ChpA C-terminal receiver domain (ChpArec). Here, we demonstrate that the ChpA Xpts are functionally divided into three categories as follows: (i) those phosphorylated with ATP (Hpt4-6); (ii) those reversibly phosphorylated by ChpArec (Hpt2-6), and (iii) those with no detectable phosphorylation (Hpt1, Spt, and Tpt). There was rapid phosphotransfer from Hpt2-6 to ChpArec and from Hpt3 to PilH, whereas transfer to PilG was slower. ChpArec also had a rapid rate of autodephosphorylation. The biochemical results together with in vivo cAMP and twitching phenotypes of key ChpA phosphorylation site point mutants supported a scheme whereby ChpArec functions both as a phosphate sink and a phosphotransfer element linking Hpt4-6 to Hpt2-3. Hpt2 and Hpt3 are likely the dominant sources of phosphoryl groups for PilG and PilH, respectively. The data are synthesized in a signaling circuit that contains fundamental features of two-component phosphorelays.
authors.affiliation: From the Department of Microbiology and Immunology and silversr@med.unc.edu.
authors.forename: Ruth E
authors.initials: RE
authors.lastname: Silversmith
authors.affiliation: Cystic Fibrosis/Pulmonary Research and Treatment Center, University of North Carolina, Chapel Hill, North Carolina 27599.
authors.forename: Boya
authors.initials: B
authors.lastname: Wang
authors.affiliation: Cystic Fibrosis/Pulmonary Research and Treatment Center, University of North Carolina, Chapel Hill, North Carolina 27599.
authors.forename: Nanette B
authors.initials: NB
authors.lastname: Fulcher
authors.affiliation: From the Department of Microbiology and Immunology and Cystic Fibrosis/Pulmonary Research and Treatment Center, University of North Carolina, Chapel Hill, North Carolina 27599.
authors.forename: Matthew C
authors.initials: MC
authors.lastname: Wolfgang
authors.affiliation: From the Department of Microbiology and Immunology and.
authors.forename: Robert B
authors.initials: RB
authors.lastname: Bourret
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000502:physiology; D010770:Phosphotransferases / Q000235:genetics / Q000378:metabolism*; D000072417:Protein Domains; D011550:Pseudomonas aeruginosa / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D010770:Phosphotransferases
keywords: Pseudomonas aeruginosa (P. aeruginosa); bacterial signal transduction; chemotaxis; histidine kinase; phosphoryl transfer; type IV pili