A hydrophobic interaction site for lysozyme binding to polyethylene glycol and model contact lens polymers.
Proton nuclear magnetic resonance (1H-NMR) spectroscopy is used to identify a preferred binding site for uncharged hydrophilic polymers on the surface of hen egg-white lysozyme. Chemical shift titrations show that exchangeable proton signals from amino acids Arg-61, Trp-62, Trp-63, Arg-73, Lys-96 and Asp-101 are selectively perturbed upon binding of poly(ethylene oxide), poly(ethylene glycol) and poly(ethylene-co-propylene oxide). The greatest binding-induced chemical shift changes are observed for Trp-62, Arg-61 and Arg-73 at the edge of the active site cleft of the protein, consistent with a predominantly hydrophobic interaction mode involving the polymer ethylene moieties. The more hydrophilic species poly(dihydroxypropyl methacrylate) causes similar but substantially smaller chemical shift effects than the other polymers, confirming the nature of the interaction. A dissociation constant of 76+/-5 mM is determined for the poly(ethylene glycol)-lysozyme complex. The relatively low affinity of the protein-polymer interactions compared to oligosaccharide substrate binding suggests that lysozyme activity is minimally affected by these materials.
School of Chemical Engineering and Industrial Chemistry, The University of New South Wales, Sydney, Australia.
E L
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Furness
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A
Ross
T P
TP
Davis
G C
GC
King
D001665:Binding Sites; D001672:Biocompatible Materials / Q000737:chemistry / Q000378:metabolism*; D003261:Contact Lenses; D007700:Kinetics; D008768:Methylmethacrylates / Q000737:chemistry / Q000378:metabolism; D009113:Muramidase / Q000737:chemistry / Q000378:metabolism*; D019906:Nuclear Magnetic Resonance, Biomolecular; D011092:Polyethylene Glycols / Q000737:chemistry / Q000378:metabolism*; D011487:Protein Conformation
C102901:2,3-dihydroxypropylmethacrylate; D001672:Biocompatible Materials; D008768:Methylmethacrylates; D011092:Polyethylene Glycols; D009113:Muramidase