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Single Molecule Force Spectroscopy Reveals Two-Domain Binding Mode of Pilus‑1 Tip Protein RrgA of Streptococcus pneumoniae to Fibronectin
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posted on 2018-03-13, 17:11 authored by Tanja
D. Becke, Stefan Ness, Raimund Gürster, Arndt F. Schilling, Anne-Marie di Guilmi, Stefanie Sudhop, Markus Hilleringmann, Hauke Clausen-SchaumannFor
host cell adhesion and invasion, surface piliation procures
benefits for bacteria. A detailed investigation of how pili adhere
to host cells is therefore a key aspect in understanding their role
during infection. Streptococcus pneumoniae TIGR 4,
a clinical relevant serotype 4 strain, is capable of expressing pilus-1
with terminal RrgA, an adhesin interacting with host extracellular
matrix (ECM) proteins. We used single molecule force spectroscopy
to investigate the binding of full-length RrgA and single RrgA domains
to fibronectin. Our results show that full-length RrgA and its terminal
domains D3 and D4 bind to fibronectin with forces of 51.6 (full length),
52.8 (D3), and 46.2 pN (D4) at force-loading rates of around 1500
pN/s. Selective saturation of D3 and D4 binding sites on fibronectin
showed that both domains can interact simultaneously with fibronectin,
revealing a two-domain binding mechanism for the pilus-1 tip protein.
The high off rates and the corresponding short lifetime of the RrgA
Fn bond (τ = 0.26 s) may enable piliated pneumococci to form
and maintain a transient contact to fibronectin-containing host surfaces
and thus to efficiently scan the surface for specific receptors promoting
host cell adhesion and invasion. These molecular properties could
be essential for S. pneumoniae pili to mediate initial
contact to the host cells andshared with other piliated Gram-positive
bacteriafavor host invasion.
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molecule force spectroscopypneumoniaeD 4 binding sitesTIGRserotype 4 strainTwo-Domain Binding Modefibronectin-containing host surfacesterminal domains D 3host cell adhesionsurface piliation procures benefitsECMRrgAD 4 bindhost cellstwo-domain binding mechanisminvasionSingle Molecule Force Spectroscopyhost extracellular matrix
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