Fig. 1
Worm-derived Trichuris muris p43 protein binds hydrophobic ligands. Binding was investigated by spectrofluorometry. (A) p43 binding of the non-specific fluorescent hydrophobic probe 8-anilino-1-naphthalenesulfonic acid (ANS) to p43 and its progressive displacement with tenfold (here and elsewhere) increasing concentrations of a natural fatty acid (oleic). (B) p43 binding of a fluorophore-tagged fatty acid analogue 11-((5-dimethylaminonaphthalene-1-sulfonyl)amino)undecanoic (DAUDA) and its near complete displacement by arachidonic acid. (C) p43 binding of a unmodified, naturally fluorescent fatty acid, cis-parinaric acid (cPnA), and its competitive displacement by oleic acid. (D) Fluorescent titration of increasing amounts of p43 added to 1.48 μM DAUDA yielding a dissociation constant (Kd) of 0.35 μM with stoichiometry indicative of two binding sites per protein molecule. Fluorescence intensity counts were converted to relative arbitrary units. The small sharp peaks at shorter wavelengths in B are from water Raman scatter. See Materials and Methods for excitations wavelengths for each fluorophore.
