Interactions of Humicola insolens cutinase with an anionic surfactant studied by small-angle neutron scattering and isothermal titration calorimetry.

摘要: The interaction of cutinase from Humicula insolens (HiC) and sodium dodecyl sulfate (SDS) has been investigated by small-angle neutron scattering (SANS) isothermal titration calorimetry (ITC). concerted interpretation structural thermodynamic information for identical systems proved valuable in attempts to elucidate the complex modes protein-detergent interaction. Particularly so at experimental temperature 22 degrees C, where formation SDS micelles is athermal (deltaH = 0), effects interactions stand out clearly thermograms. It was found that effect on depended strongly sample composition. Thus, addition corresponding a molar ratio, n(s) n(SDS)/n(HiC) about 10, associated with HiC/SDS aggregates, which include more than one protein molecule. SANS results suggested average such adducts contained two HiC, ITC traces showed they form break down slowly. At slightly higher concentrations (n(s) 10-25) these "dimers" dissociated, denatured. denaturation characteristic positive enthalpy change, but denatured state HiC unusually compact radius gyration close native conformation. Further exothermic binding until saturation point 90. this point, free monomer concentration 2.2 mM number approximately 40 SDS/HiC. Interestingly, degree (approximately 0.5 g SDS/g HiC) less half amount bound typical water-soluble proteins.