Interplay of a secreted protein with type IVb pilus for efficient enterotoxigenic
            <i>Escherichia coli</i>
            colonization

Oki, Hiroya; Kawahara, Kazuki; Maruno, Takahiro; Imai, Tomoya; Muroga, Yuki; Fukakusa, Shunsuke; Iwashita, Takaki; Kobayashi, Yuji; Matsuda, Shigeaki; Kodama, Takao; Iida, Tetsuya; Yoshida, Takuya; Ohkubo, Tadayasu; Nakamura, Shota

doi:10.1073/pnas.1805671115

Cited by 19 publications

(23 citation statements)

References 52 publications

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“…We hypothesize that the relevant adhesin in this case is not PilA itself but a minor pilin subunit (consistent with the conservation we see of the minor A. baumannii minor pilins in Fig. 1) or a protein that interacts with the pilus, either constitutively at the tip (76) or as a secreted factor, as was recently shown in the type IVb pili of ETEC (77).…”

Section: Functional Specialization In Acinetobacter Type IV Pilisupporting

confidence: 87%

The structure of PilA from Acinetobacter baumannii AB5075 suggests a mechanism for functional specialization in Acinetobacter type IV pili

Ronish

Lillehoj

Fields

et al. 2019

Journal of Biological Chemistry

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Type IV pili (T4P) are bacterial appendages composed of protein subunits, called pilins, noncovalently assembled into helical fibers. T4P are essential, in many bacterial species, for processes as diverse as twitching motility, natural competence, biofilm or microcolony formation, and host cell adhesion. The genes encoding type IV pili are found universally in the Gram-negative, aerobic, nonflagellated, and pathogenic coccobacillus Acinetobacter baumannii, but there is considerable variation in PilA, the major protein subunit, both in amino acid sequence and in glycosylation patterns. Here we report the X-ray crystal structure of PilA from AB5075, a recently characterized, highly virulent isolate, at 1.9 Å resolution and compare it to homologues from A. baumannii strains ACICU and BIDMC57, which are C-terminally glycosylated. These structural comparisons revealed that PilA AB5075 exhibits a distinctly electronegative surface chemistry. To understand the functional consequences of this change in surface electrostatics, we complemented a ⌬pilA knockout strain with divergent pilA genes from ACICU, BIDMC57, and AB5075. The resulting transgenic strains showed differential twitching motility and biofilm formation while maintaining the ability to adhere to epithelial cells. PilA AB5075 and PilA ACICU , although structurally similar, promote different characteristics, favoring twitching motility and biofilm formation, respectively. These results support a model in which differences in pilus electrostatics affect the equilibrium of microcolony formation, which in turn alters the balance between motility and biofilm formation in Acinetobacter. 2 The abbreviations used are: T4P, type IV pili; CLSM, confocal laser scanning microscopy.

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Section: Functional Specialization In Acinetobacter Type IV Pilisupporting

confidence: 87%

The structure of PilA from Acinetobacter baumannii AB5075 suggests a mechanism for functional specialization in Acinetobacter type IV pili

Ronish

Lillehoj

Fields

et al. 2019

Journal of Biological Chemistry

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“…9). A similar mechanism has been recently described for a T4b pilus from enterotoxicogenic E. coli, where a secreted adhesin (CofJ) protein functions as a type of "scout" that first associates with receptors on the host cell and subsequently interacts with minor pilins present at the tip of the T4b pilus (53). Future studies to confirm the interaction of ta pirin proteins with T4 pilins from the genus Caldicellulosiruptor are under way.…”

Section: Discussionsupporting

confidence: 52%

Caldicellulosiruptor bescii Adheres to Polysaccharides via a Type IV Pilin-Dependent Mechanism

Khan

Hauk

et al. 2020

Appl Environ Microbiol

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Biological hydrolysis of cellulose above 70°C involves microorganisms that secrete free enzymes and deploy separate protein systems to adhere to their substrate. Strongly cellulolytic Caldicellulosiruptor bescii is one such extreme thermophile, which deploys modular, multifunctional carbohydrate-acting enzymes to deconstruct plant biomass. Additionally, C. bescii also encodes noncatalytic carbohydrate binding proteins, which likely evolved as a mechanism to compete against other heterotrophs in carbon-limited biotopes that these bacteria inhabit. Analysis of the Caldicellulosiruptor pangenome identified a type IV pilus (T4P) locus encoded upstream of the tāpirins, that is encoded by all Caldicellulosiruptor species. In this study, we sought to determine if the C. bescii T4P plays a role in attachment to plant polysaccharides. The major C. bescii pilin (CbPilA) was identified by the presence of pilin-like protein domains, paired with transcriptomics and proteomics data. Using immuno-dot blots, we determined that the plant polysaccharide xylan induced production of CbPilA 10- to 14-fold higher than glucomannan or xylose. Furthermore, we are able to demonstrate that recombinant CbPilA directly interacts with xylan and cellulose at elevated temperatures. Localization of CbPilA at the cell surface was confirmed by immunofluorescence microscopy. Lastly, a direct role for CbPilA in cell adhesion was demonstrated using recombinant CbPilA or anti-CbPilA antibodies to reduce C. bescii cell adhesion to xylan and crystalline cellulose up to 4.5- and 2-fold, respectively. Based on these observations, we propose that CbPilA and, by extension, the T4P play a role in Caldicellulosiruptor cell attachment to plant biomass. IMPORTANCE Most microorganisms are capable of attaching to surfaces in order to persist in their environment. Type IV (T4) pili produced by certain mesophilic Firmicutes promote adherence; however, a role for T4 pili encoded by thermophilic members of this phylum has yet to be demonstrated. Prior comparative genomics analyses identified a T4 pilus locus possessed by an extremely thermophilic genus within the Firmicutes. Here, we demonstrate that attachment to plant biomass-related carbohydrates by strongly cellulolytic Caldicellulosiruptor bescii is mediated by T4 pilins. Surprisingly, xylan but not cellulose induced expression of the major T4 pilin. Regardless, the C. bescii T4 pilin interacts with both polysaccharides at high temperatures and is located to the cell surface, where it is directly involved in C. bescii attachment. Adherence to polysaccharides is likely key to survival in environments where carbon sources are limiting, allowing C. bescii to compete against other plant-degrading microorganisms.

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“…For example, in CofB from enterotoxigenic E. coli (ETEC) T4bP, there are two additional structural domains linked to the C terminus of the pilin module by a flexible linker, a β-repeat domain followed by a β-sandwich domain ( 30 ). CofB, which forms a trimer predicted to be exposed at the tip of ETEC T4bP ( 31 ), appears to be an adapter for a secreted protein CofJ ( 32 ) that has a direct role in adhesion. TcpB, from Vibrio cholerae T4bP toxin-coregulated pilus, is a tip-located minor pilin forming trimers with a structure very similar to CofB ( 33 ), which probably has a similar function.…”

Section: Discussionmentioning

confidence: 99%

PilB from Streptococcus sanguinis is a bimodular type IV pilin with a direct role in adhesion

Raynaud

Sheppard

Berry

et al. 2021

Proc. Natl. Acad. Sci. U.S.A.

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Type IV pili (T4P) are functionally versatile filamentous nanomachines, nearly ubiquitous in prokaryotes. They are predominantly polymers of one major pilin but also contain minor pilins whose functions are often poorly defined and likely to be diverse. Here, we show that the minor pilin PilB from the T4P of Streptococcus sanguinis displays an unusual bimodular three-dimensional structure with a bulky von Willebrand factor A–like (vWA) module “grafted” onto a small pilin module via a short loop. Structural modeling suggests that PilB is only compatible with a localization at the tip of T4P. By performing a detailed functional analysis, we found that 1) the vWA module contains a canonical metal ion–dependent adhesion site, preferentially binding Mg2+ and Mn2+, 2) abolishing metal binding has no impact on the structure of PilB or piliation, 3) metal binding is important for S. sanguinis T4P–mediated twitching motility and adhesion to eukaryotic cells, and 4) the vWA module shows an intrinsic binding ability to several host proteins. These findings reveal an elegant yet simple evolutionary tinkering strategy to increase T4P functional versatility by grafting a functional module onto a pilin for presentation by the filaments. This strategy appears to have been extensively used by bacteria, in which modular pilins are widespread and exhibit an astonishing variety of architectures.

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Interplay of a secreted protein with type IVb pilus for efficient enterotoxigenic Escherichia coli colonization

Cited by 19 publications

References 52 publications

The structure of PilA from Acinetobacter baumannii AB5075 suggests a mechanism for functional specialization in Acinetobacter type IV pili

The structure of PilA from Acinetobacter baumannii AB5075 suggests a mechanism for functional specialization in Acinetobacter type IV pili

Caldicellulosiruptor bescii Adheres to Polysaccharides via a Type IV Pilin-Dependent Mechanism

PilB from Streptococcus sanguinis is a bimodular type IV pilin with a direct role in adhesion

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