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Title: The Escherichia coli P and Type 1 Pilus Assembly Chaperones PapD and FimC Are Monomeric in Solution

Abstract

ABSTRACT The chaperone/usher pathway is used by Gram-negative bacteria to assemble adhesive surface structures known as pili or fimbriae. Uropathogenic strains ofEscherichia coliuse this pathway to assemble P and type 1 pili, which facilitate colonization of the kidney and bladder, respectively. Pilus assembly requires a periplasmic chaperone and outer membrane protein termed the usher. The chaperone allows folding of pilus subunits and escorts the subunits to the usher for polymerization into pili and secretion to the cell surface. Based on previous structures of mutant versions of the P pilus chaperone PapD, it was suggested that the chaperone dimerizes in the periplasm as a self-capping mechanism. Such dimerization is counterintuitive because the chaperone G1 strand, important for chaperone-subunit interaction, is buried at the dimer interface. Here, we show that the wild-type PapD chaperone also forms a dimer in the crystal lattice; however, the dimer interface is different from the previously solved structures. In contrast to the crystal structures, we found that both PapD and the type 1 pilus chaperone, FimC, are monomeric in solution. Our findings indicate that pilus chaperones do not sequester their G1 β-strand by forming a dimer. Instead, the chaperones may expose their G1 strand for facile interactionmore » with pilus subunits. We also found that the type 1 pilus adhesin, FimH, is flexible in solution while in complex with its chaperone, whereas the P pilus adhesin, PapGII, is rigid. Our study clarifies a crucial step in pilus biogenesis and reveals pilus-specific differences that may relate to biological function. IMPORTANCEPili are critical virulence factors for many bacterial pathogens. UropathogenicE. colirelies on P and type 1 pili assembled by the chaperone/usher pathway to adhere to the urinary tract and establish infection. Studying pilus assembly is important for understanding mechanisms of protein secretion, as well as for identifying points for therapeutic intervention. Pilus biogenesis is a multistep process. This work investigates the oligomeric state of the pilus chaperone in the periplasm, which is important for understanding early assembly events. Our work unambiguously demonstrates that both PapD and FimC chaperones are monomeric in solution. We further demonstrate that the solution behavior of the FimH and PapGII adhesins differ, which may be related to functional differences between the two pilus systems.« less

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1354585
Report Number(s):
BNL-113102-2016-JA
Journal ID: ISSN 0021-9193
DOE Contract Number:  
SC00112704
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Bacteriology; Journal Volume: 198; Journal Issue: 17
Country of Publication:
United States
Language:
English

Citation Formats

Sarowar, Samema, Hu, Olivia J., Werneburg, Glenn T., Thanassi, David G., Li, Huilin, and Christie, P. J.. The Escherichia coli P and Type 1 Pilus Assembly Chaperones PapD and FimC Are Monomeric in Solution. United States: N. p., 2016. Web. doi:10.1128/JB.00366-16.
Sarowar, Samema, Hu, Olivia J., Werneburg, Glenn T., Thanassi, David G., Li, Huilin, & Christie, P. J.. The Escherichia coli P and Type 1 Pilus Assembly Chaperones PapD and FimC Are Monomeric in Solution. United States. doi:10.1128/JB.00366-16.
Sarowar, Samema, Hu, Olivia J., Werneburg, Glenn T., Thanassi, David G., Li, Huilin, and Christie, P. J.. Mon . "The Escherichia coli P and Type 1 Pilus Assembly Chaperones PapD and FimC Are Monomeric in Solution". United States. doi:10.1128/JB.00366-16.
@article{osti_1354585,
title = {The Escherichia coli P and Type 1 Pilus Assembly Chaperones PapD and FimC Are Monomeric in Solution},
author = {Sarowar, Samema and Hu, Olivia J. and Werneburg, Glenn T. and Thanassi, David G. and Li, Huilin and Christie, P. J.},
abstractNote = {ABSTRACT The chaperone/usher pathway is used by Gram-negative bacteria to assemble adhesive surface structures known as pili or fimbriae. Uropathogenic strains ofEscherichia coliuse this pathway to assemble P and type 1 pili, which facilitate colonization of the kidney and bladder, respectively. Pilus assembly requires a periplasmic chaperone and outer membrane protein termed the usher. The chaperone allows folding of pilus subunits and escorts the subunits to the usher for polymerization into pili and secretion to the cell surface. Based on previous structures of mutant versions of the P pilus chaperone PapD, it was suggested that the chaperone dimerizes in the periplasm as a self-capping mechanism. Such dimerization is counterintuitive because the chaperone G1 strand, important for chaperone-subunit interaction, is buried at the dimer interface. Here, we show that the wild-type PapD chaperone also forms a dimer in the crystal lattice; however, the dimer interface is different from the previously solved structures. In contrast to the crystal structures, we found that both PapD and the type 1 pilus chaperone, FimC, are monomeric in solution. Our findings indicate that pilus chaperones do not sequester their G1 β-strand by forming a dimer. Instead, the chaperones may expose their G1 strand for facile interaction with pilus subunits. We also found that the type 1 pilus adhesin, FimH, is flexible in solution while in complex with its chaperone, whereas the P pilus adhesin, PapGII, is rigid. Our study clarifies a crucial step in pilus biogenesis and reveals pilus-specific differences that may relate to biological function. IMPORTANCEPili are critical virulence factors for many bacterial pathogens. UropathogenicE. colirelies on P and type 1 pili assembled by the chaperone/usher pathway to adhere to the urinary tract and establish infection. Studying pilus assembly is important for understanding mechanisms of protein secretion, as well as for identifying points for therapeutic intervention. Pilus biogenesis is a multistep process. This work investigates the oligomeric state of the pilus chaperone in the periplasm, which is important for understanding early assembly events. Our work unambiguously demonstrates that both PapD and FimC chaperones are monomeric in solution. We further demonstrate that the solution behavior of the FimH and PapGII adhesins differ, which may be related to functional differences between the two pilus systems.},
doi = {10.1128/JB.00366-16},
journal = {Journal of Bacteriology},
number = 17,
volume = 198,
place = {United States},
year = {Mon Jun 27 00:00:00 EDT 2016},
month = {Mon Jun 27 00:00:00 EDT 2016}
}