title: Differential scanning calorimetry of alpha 2-macroglobulin and alpha 2-macroglobulin-proteinase complexes.
abstract: Differential scanning calorimetry is shown to detect substantial structural alterations occurring on the association of proteinases with the serum glycoprotein alpha 2-macroglobulin. At pH 7.5, the thermally induced unfolding of the macroglobulin occurs at approx. 60 degrees C with a transition enthalpy of 17 J/g. Association of active thermolysin, trypsin and papain shifts the transition temperature to 77 degrees C (transition enthalpy 5 J/g), indicating that a substantial conformational change accompanies the binding event. The stoicheiometry of the thermolysin--alpha 2-macroglobulin association producing this change appears to be unity, implying the presence of co-operative subunit interactions in the mechanism of association. The calorimetric method provides a novel approach for the evaluation of conformational variants induced on protein-protein association or pre-existing in the purified macroglobulin.
mesh_terms: D002152:Calorimetry, Differential Scanning; D010450:Endopeptidases / Q000378:metabolism*; D046911:Macromolecular Substances; D010206:Papain / Q000378:metabolism; D011487:Protein Conformation; D013816:Thermodynamics; D013820:Thermolysin / Q000378:metabolism; D014357:Trypsin / Q000378:metabolism; D000511:alpha-Macroglobulins / Q000378:metabolism*
chemical_list: D046911:Macromolecular Substances; C038528:alpha-2-macroglobulin-thermolysin complex; C028939:alpha-2-macroglobulin-trypsin complex; D000511:alpha-Macroglobulins; D010450:Endopeptidases; D014357:Trypsin; D010206:Papain; D013820:Thermolysin