Structural basis for usher activation and intramolecular subunit transfer in P pilus biogenesis in Escherichia coli

Omattage, Natalie S.; Deng, Zhichao; Pinkner, Jerome S.; Dodson, Karen W.; Almqvist, Fredrik; Yuan, Peng; Hultgren, Scott J.

doi:10.1038/s41564-018-0255-y

“…Two recent structures are beginning to shed light onto the handover mechanism of chaperone-subunit complexes from the NTD to the CTDs. First, a crystal structure of the "pre-activated" PapC usher, in complex with the chaperone-adhesin complex (PapDG), was determined (33) (Fig. 1d).…”

Section: Biogenesis Of Chaperone-usher Pilimentioning

confidence: 99%

The Remarkable Biomechanical Properties of the Type 1 Chaperone-Usher Pilus: A Structural and Molecular Perspective

Hospenthal

¹

,

Waksman

²

2019

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Chaperone-usher (CU) pili are long, supramolecular protein fibers tethered to the surface of numerous bacterial pathogens. These virulence factors function primarily in bacterial adhesion to host tissues, but they also mediate biofilm formation. Type 1 and P pili of uropathogenic Escherichia coli (UPEC) are the two best-studied CU pilus examples, and here we primarily focus on the former. UPEC can be transmitted to the urinary tract by fecal shedding. It can then ascend up the urinary tract and cause disease by invading and colonizing host tissues of the bladder, causing cystitis, and the kidneys, causing pyelonephritis. FimH is the subunit displayed at the tip of type 1 pili and mediates adhesion to mannosylated host cells via a unique catch-bond mechanism. In response to shear forces caused by urine flow, FimH can transition from a low-affinity to high-affinity binding mode. This clever allosteric mechanism allows UPEC cells to remain tightly attached during periods of urine flow, while loosening their grip to allow dissemination through the urinary tract during urine stasis. Moreover, the bulk of a CU pilus is made up of the rod, which can reversibly uncoil in response to urine flow to evenly spread the tensile forces over the entire pilus length. We here explore the novel structural and mechanistic findings relating to the type 1 pilus FimH catch-bond and rod uncoiling and explain how they function together to enable successful attachment, spread, and persistence in the hostile urinary tract.

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“…3, 4, Extended Data Table 1). Crystal structures are available for each of the proteins in the Pap complexes 8,10,17,25 , which allowed for atomic models to be built with confidence at these resolutions for most parts of the cryo-EM maps, with remaining parts built de novo with the help of large aromatic residues (Trp, Tyr, Phe and His) ( Fig. 2a-c, Extended Data Fig.…”

Section: Cryo-em Reveals Three Conformationsmentioning

confidence: 99%

“…Ushers contain five domains: a central 24-stranded ß-barrel domain that inserts into the OM to form the secretion channel, an internal plug domain that forms the channel gate, a periplasmic N-terminal domain (NTD) that functions in subunit recruitment, and two tandem periplasmic Cterminal domains (CTD1 and CTD2) that function in pilus assembly and secretion [14][15][16][17] . In the inactive, apo usher, the plug domain is located within the ß-barrel pore, closing the channel, and the NTD resides free in the periplasm, ready to recruit chaperone-subunit complexes (Fig.1b).…”

Section: Introductionmentioning

confidence: 99%

Processive Dynamics of the Usher Assembly Platform During UropathogenicEscherichia coliP Pilus Biogenesis

Du

¹

,

Yuan

²

,

Werneburg

³

et al. 2020

Preprint

0

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Uropathogenic Escherichia coli (UPEC) assemble hair-like surface structures termed pili or fimbriae to initiate infection of the urinary tract. P pili mediate the adherence of UPEC to the kidney epithelium, facilitating bacterial colonization and pyelonephritis1. P pili are assembled through the conserved chaperone-usher (CU) pathway2-4. In this pathway, a dedicated chaperone facilitates the folding of nascent pilus subunits in the periplasm and an integral outer membrane (OM) protein termed the usher provides the assembly platform and secretion channel for the pilus fiber. Much of the structural and functional understanding of the CU pathway has been gained through investigations of type 1 pili, which promote UPEC binding to the bladder epithelium and the development of cystitis5. In contrast, the structural basis for P pilus biogenesis at the usher has remained elusive. This is in part due to the flexible and variable-length P pilus tip fiber, creating structural heterogeneity, as well as difficulties in isolating stable P pilus assembly intermediates from bacteria. Here, we have devised a method to circumvent these hindrances and determined cryo-EM structures of the activated PapC usher in the process of secreting two- and three-subunit P pilus assembly intermediates. These structures show processive steps in P pilus biogenesis, reveal differences between P and type 1 pili, and capture new conformational dynamics of the usher assembly machine.

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“…(d and e) Two novel structures shed light on the chaperone-subunit handover mechanism from the NTD to the CTDs. Shown are the structures of PapCDG (PDB code 6CD2 [33]) in a preactivated state (d) and of FimDCFGH (PDB code 6E14 [34]) in an activated state (e), trapping conformations that show novel interactions between the NTD and CTD2, during chaperone-subunit handover. Dashed boxes and zoomed-in views highlight the NTD to CTD2 interactions.…”

Section: Clinging On: the Importance Of The Pilus Rodmentioning

confidence: 99%

The Remarkable Biomechanical Properties of the Type 1 Chaperone-Usher Pilus: A Structural and Molecular Perspective

Hospenthal

¹

,

Waksman

²

2019

Protein Secretion in Bacteria

View full text Add to dashboard Cite

Chaperone-usher (CU) pili are long, supramolecular protein fibers tethered to the surface of numerous bacterial pathogens. These virulence factors function primarily in bacterial adhesion to host tissues, but they also mediate biofilm formation. Type 1 and P pili of uropathogenic Escherichia coli (UPEC) are the two best-studied CU pilus examples, and here we primarily focus on the former. UPEC can be transmitted to the urinary tract by fecal shedding. It can then ascend up the urinary tract and cause disease by invading and colonizing host tissues of the bladder, causing cystitis, and the kidneys, causing pyelonephritis. FimH is the subunit displayed at the tip of type 1 pili and mediates adhesion to mannosylated host cells via a unique catch-bond mechanism. In response to shear forces caused by urine flow, FimH can transition from a low-affinity to high-affinity binding mode. This clever allosteric mechanism allows UPEC cells to remain tightly attached during periods of urine flow, while loosening their grip to allow dissemination through the urinary tract during urine stasis. Moreover, the bulk of a CU pilus is made up of the rod, which can reversibly uncoil in response to urine flow to evenly spread the tensile forces over the entire pilus length. We here explore the novel structural and mechanistic findings relating to the type 1 pilus FimH catch-bond and rod uncoiling and explain how they function together to enable successful attachment, spread, and persistence in the hostile urinary tract.

show abstract

Structural basis for usher activation and intramolecular subunit transfer in P pilus biogenesis in Escherichia coli

Cited by 20 publications

References 49 publications

The Remarkable Biomechanical Properties of the Type 1 Chaperone-Usher Pilus: A Structural and Molecular Perspective

The Remarkable Biomechanical Properties of the Type 1 Chaperone-Usher Pilus: A Structural and Molecular Perspective

Processive Dynamics of the Usher Assembly Platform During UropathogenicEscherichia coliP Pilus Biogenesis

The Remarkable Biomechanical Properties of the Type 1 Chaperone-Usher Pilus: A Structural and Molecular Perspective

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