Streptococcus pneumoniae Type 1 Pilus – A Multifunctional Tool for Optimized Host Interaction

Ness, Stefan; Hilleringmann, Markus

doi:10.3389/fmicb.2021.615924

Cited by 6 publications

(14 citation statements)

References 77 publications

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“…We further confirmed a possible binding specificity for galactose and fucose (greater with the former than the latter) in the D2 (vWFA) domain via glycan microarray screening. Here, it is worth mentioning that the RrgA tip pilin was shown to bind various glycans, including galactose [61,62]. Remarkably, we were able to show and validate that the PitA tip pilin (via the PI-2 pilus) forms an interaction with the CafA tip pilin (via the type 2 pilus) during the coaggregation of S. oralis and A. oris cells.…”

Section: Discussionsupporting

confidence: 65%

New structural insights into the PI‐2 pilus from Streptococcus oralis, an early dental plaque colonizer

Yadav

Krishnan

2022

The FEBS Journal

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Streptococcus oralis is a member of the mitis group of oral streptococci and an early colonizer in dental plaque biofilm, a major cause of periodontal disease, dental caries, and other oral infections. S. oralis promotes biofilm growth by coaggregating in a mutualistic partnership with other early colonizers such as Actinomyces oris. For this cell‐to‐cell interaction, A. oris is known to use its sortase‐dependent pilus (type 2), but whether S. oralis uses its PI‐2 (pilus islet 2) pilus is still to be determined. The PI‐2 pilus is predicted to have a heterodimeric structure consisting of two different protein subunits with their own location and function: the tip PitA pilin for adhesion and the backbone PitB pilin for length. Thus far, structural information remains incomplete about the role of PI‐2 pili in the mutualistic mechanism between S. oralis and A. oris. We now report on the crystal structure analysis of PitA and PitB using X‐ray crystallography, small‐angle X‐ray scattering, and molecular docking studies. Accordingly, we propose a structural model for the PI‐2 pilus, wherein repeating PitB subunits are arranged head‐to‐tail to form the long backbone structure with PitA on the outer tip. By performing both in vitro and in vivo experiments, we examined the role played by PitA in mediating the mutualistic interaction between S. oralis and A. oris, which appears to involve the coaggregation factor CafA. We also reveal that the galactose monosaccharide is a conceivable ligand for PitA and thereby might be used to inhibit coaggregation and control oral biofilm development. Database Structural coordinates for the PitA fragment, PitA fragment TbXO4 derivative, full‐length PitA, and PitB from S. oralis have been deposited at the Protein Data Bank as 7VCR, 7W7I, 7VCN, 7W6B, and 7W7I, respectively. Streptococcus pneumoniae PitB coordinates have been deposited as 7F7Y.

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Section: Discussionsupporting

confidence: 65%

New structural insights into the PI‐2 pilus from Streptococcus oralis, an early dental plaque colonizer

Yadav

Krishnan

2022

The FEBS Journal

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“…87 Most streptococcal cell surface proteins possess a cell wall-anchored motif (typically Leu-Pro-x-Thr-Gly [LPxTG]) in the C-terminal regions. [88][89][90] Sortases are transpeptidases that catalyze the attachment of proteins covalently to cell wall components via the LPxTG motif. [88][89][90] This type of enzymes also catalyzes the assembly of pilus subunits into pili, long filamentous structures with a pilus polymer backbone (see the next section).…”

Section: Cell Surface Proteins and Enzymes (1): Matrix-binding Proteinsmentioning

confidence: 99%

“…Pili of these streptococci consist of a pilus major backbone subunit, with one or more minor pilus subunits that are covalently assembled on the cell surface by the action of pilus-associated sortases. 45,46,88,90 The pilus islets in the genomes of these streptococci are composed of genes encoding multiple pilus subunits carrying the LPxTG motif together with genes for sortases. 45,46,[88][89][90] The pili of pathogenic streptococci serve as adhesins in host cells.…”

Section: Cell Surface Proteins and Enzymes (2): Pilimentioning

confidence: 99%

“…45,46,88,90 The pilus islets in the genomes of these streptococci are composed of genes encoding multiple pilus subunits carrying the LPxTG motif together with genes for sortases. 45,46,[88][89][90] The pili of pathogenic streptococci serve as adhesins in host cells. 45,46,89,90 S. pneumoniae has two types of pilus islets: pilus islet 1 (PI-1), which is composed of three pilus subunits and three sortases; and pilus islet 2 (PI-2), which is composed of two pilus subunit, two sortases, and signal peptidase-like protein SipA.…”

Section: Cell Surface Proteins and Enzymes (2): Pilimentioning

confidence: 99%

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Oral mitis group streptococci: A silent majority in our oral cavity

Okahashi

Nakata

Kuwata

et al. 2022

Microbiology and Immunology

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Members of the oral mitis group streptococci including Streptococcus oralis, Streptococcus sanguinis, and Streptococcus gordonii are the most abundant inhabitants of human oral cavity and dental plaque, and have been implicated in infectious complications such as bacteremia and infective endocarditis. Oral mitis group streptococci are genetically close to Streptococcus pneumoniae; however, they do not produce cytolysin (pneumolysin), which is a key virulence factor of S. pneumoniae. Similar to S. pneumoniae, oral mitis group streptococci possess several cell surface proteins that bind to the cell surface components of host mammalian cells. S. sanguinis expresses long filamentous pili that bind to the matrix proteins of host cells. The cell wall–anchored nuclease of S. sanguinis contributes to the evasion of the neutrophil extracellular trap by digesting its web‐like extracellular DNA. Oral mitis group streptococci produce glucosyltransferases, which synthesize glucan (glucose polymer) from sucrose of dietary origin. Neuraminidase (NA) is a virulent factor in oral mitis group streptococci. Influenza type A virus (IAV) relies on viral NA activity to release progeny viruses from infected cells and spread the infection, and NA‐producing oral streptococci elevate the risk of IAV infection. Moreover, oral mitis group streptococci produce hydrogen peroxide (H2O2) as a by‐product of sugar metabolism. Although the concentrations of streptococcal H2O2 are low (1–2 mM), they play important roles in bacterial competition in the oral cavity and evasion of phagocytosis by host macrophages and neutrophils. In this review, we intended to describe the diverse pathogenicity of oral mitis group streptococci.

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“…Two types of pili have been identified in S. pneumoniae : type 1 encoded by Pilus Islet 1 (PI-1) [ 4 , 11 ] and type 2 encoded by Pilus Islet 2 (PI-2) [ 12 ]. Both pili are polymers of major- and minor-pilus proteins covalently linked and anchored to the cell surface [ 13 ]. Molecular epidemiology studies showed that only a small proportion of the pneumococcal population harbors pili-encoding genes in their genomes.…”

Section: Introductionmentioning

confidence: 99%

A Small Non-Coding RNA Modulates Expression of Pilus-1 Type in Streptococcus pneumoniae

et al. 2021

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Streptococcus pneumoniae is a major cause of morbidity and mortality worldwide, and about 30% of the pneumococcal clinical isolates show type I pili-like structures. These long proteinaceous polymers extending from the bacterial surface are encoded by pilus islet 1 and play major roles in adhesion and host colonization. Pili expression is bistable and is controlled by the transcriptional activator RlrA. In this work, we demonstrate that the previously identified small noncoding RNA srn135 also participates in pilus regulation. Our findings show that srn135 is generated upon processing of the 5′-UTR region of rrgA messenger and its deletion prevents the synthesis of RrgA, the main pili adhesin. Moreover, overexpression of srn135 increases the expression of all pili genes and rises the percentage of piliated bacteria within a clonal population. This regulation is mediated by the stabilization of rlrA mRNA since higher levels of srn135 increase its half-life to 165%. Our findings suggest that srn135 has a dual role in pilus expression acting both in cis- (on the RrgA levels) and in trans- (modulating the levels of RlrA) and contributes to the delicate balance between pili expressing and non-expressing bacteria.

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Streptococcus pneumoniae Type 1 Pilus – A Multifunctional Tool for Optimized Host Interaction

Cited by 6 publications

References 77 publications

New structural insights into the PI‐2 pilus from Streptococcus oralis, an early dental plaque colonizer

New structural insights into the PI‐2 pilus from Streptococcus oralis, an early dental plaque colonizer

Oral mitis group streptococci: A silent majority in our oral cavity

A Small Non-Coding RNA Modulates Expression of Pilus-1 Type in Streptococcus pneumoniae

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