tonB3 Is Required for Normal Twitching Motility and Extracellular Assembly of Type IV Pili

Abstract

Three mutants with Tn5-B21 insertion in tonB3 (PA0406) of Pseudomonas aeruginosa exhibited defective twitching motility and reduced assembly of extracellular pili. These defects could be complemented with wild-type tonB3

ExbBD-Dependent Transport of Maltodextrins through the Novel MalA Protein across the Outer Membrane ofCaulobacter crescentus

“…The predicted TonB protein shows 26.1% sequence identity to E. coli TonB, contains an N-proximal transmembrane segment with a histidine residue at a position equivalent to that of the functionally important His-20 of E. coli TonB (59) but lacks the functionally important Ser-16 (36). It also contains a number of proline residues that are thought to play a role in spanning the periplasmic space (29,37). However, the sequence around Gln-160, which in E. coli TonB interacts with outer membrane transporters (27,52), is very different in C. crescentus TonB.…”

“…This protein might function as TonB or substitute for the examined TonB in maltopentaose and maltoheptaose transport when TonB is lacking. Several TonB proteins which can completely or partially functionally substitute for each other have been found in various other organisms, e.g., Serratia marcescens (42), Vibrio cholerae (54), and Pseudomonas aeruginosa (29,63). The function of the 401-residue protein is currently being investigated.…”

Identification and characterization of an iron-regulated gene, chtA, required for the utilization of the xenosiderophores aerobactin, rhizobactin 1021 and schizokinen by Pseudomonas aeruginosa

“…Three TonB homologues, TonB1, TonB2 and TonB3, have been identified in the P. aeruginosa genome sequence and all three homologues have been experimentally characterized Takase et al, 2000;Zhao & Poole, 2000Huang et al, 2004). Siderophore-mediated iron transport in P. aeruginosa is primarily dependent on the activity of the TonB1 protein.…”

“…A second tonB gene, tonB2, identified in P. aeruginosa is linked to homologues of exbB and exbD; however, the TonB2 protein and the ExbB and ExbD proteins were found to be dispensable for iron acquisition (Zhao & Poole, 2000). A third tonB gene, termed tonB3, was found to be required for normal twitching motility and the assembly of extracellular pili (Huang et al, 2004). Little is known about the mechanisms of inner-membrane siderophore transport in P. aeruginosa.…”

Interaction of TonB with the Outer Membrane Receptor FpvA ofPseudomonas aeruginosa

“…Inactivation of tonB2 has no adverse effect on iron or heme acquisition, but tonB1-tonB2 double mutants are more compromised with respect to growth in iron-restricted medium than is a single tonB1 knockout mutant (55). Inactivation of tonB3 appears to result in a defective twitching motility (19), and the gene product is most likely not involved in iron uptake. Most knowledge about TonB function and structure has been obtained primarily from studies with Escherichia coli TonB (reviewed in reference 40).…”