AVS 52nd International Symposium
    Biomaterial Interfaces Wednesday Sessions
       Session BI1-WeM

Paper BI1-WeM10
Binding of the Streptococcal C5a Peptidase to Immobilized Fibronectin

Wednesday, November 2, 2005, 11:20 am, Room 311

Session: Protein-Surface Interactions
Presenter: J.R. Hull, University of Washington
Authors: J.R. Hull, University of Washington
G. Tamura, The University of Washington Dept. of Pediatrics
D.G. Castner, University of Washington
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Group B Streptococci (GBS) are a leading cause of sepsis and meningitis in newborns, and an emerging cause of serious bacterial infections in immunocompromised adults and the elderly. The streptococcal C5a peptidase (ScpB) of GBS is found in virtually all clinical isolates of GBS. ScpB inhibits neutrophil chemotaxis by enzymatically cleaving the complement component C5a. ScpB is a known Fibronectin (Fn) adhesin; however, it only binds to immobilized Fn and not soluble Fn. Therefore, it is unknown whether or not ScpB binds to a conformational determinate of Fn or multiple adjacent Fn molecules. For this study, surface plasmon resonance (SPR) was used to determine the affinity of ScpB for immobilized Fn. The measured affinity is in the nM range, which is biologically significant. ScpB was tethered to an atomic force microscope (AFM) tip via the bifunctional cross linker pyridyldithio poly(ethylene glycol) succinimidylpropionate (NHS-PEG-PDP). Each step of the tip functionalization was verified by X-ray photoelectron spectroscopy, static secondary ion mass spectrometry, and infrared spectroscopy. Adsorbed Fn was imaged via intermittent contact AFM with the ScpB modified tip at varying surface concentrations. Then force-distance curves were used to measure the interactions between ScpB and adsorbed Fn.