Structural insight into the role of Streptococcus parasanguinis Fap1 within oral biofilm formation |
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Authors: | Garnett James A Simpson Peter J Taylor Jonathan Benjamin Stefi V Tagliaferri Camille Cota Ernesto Chen Yi-Ywan M Wu Hui Matthews Stephen |
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Affiliation: | Department of Biological Sciences, Centre for Structural Biology, Imperial College London, London, UK. |
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Abstract: | The fimbriae-associated protein 1 (Fap1) is a major adhesin of Streptococcus parasanguinis, a primary colonizer of the oral cavity that plays an important role in the formation of dental plaque. Fap1 is an extracellular adhesive surface fibre belonging to the serine-rich repeat protein (SRRP) family, which plays a central role in the pathogenesis of streptococci and staphylococci. The N-terminal adhesive region of Fap1 (Fap1-NR) is composed of two domains (Fap1-NRα and Fap1-NRβ) and is projected away from the bacterial surface via the extensive serine-rich repeat region, for adhesion to the salivary pellicle. The adhesive properties of Fap1 are modulated through a pH switch in which a reduction in pH results in a rearrangement between the Fap1-NRα and Fap1-NRβ domains, which assists in the survival of S. parasanguinis in acidic environments. We have solved the structure of Fap1-NRα at pH 5.0 at 3.0 ? resolution and reveal how subtle rearrangements of the 3-helix bundle combined with a change in electrostatic potential mediates ‘opening’ and activation of the adhesive region. Further, we show that pH-dependent changes are critical for biofilm formation and present an atomic model for the inter-Fap1-NR interactions which have been assigned an important role in the biofilm formation. |
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