Effect of methylamine and plasmin on the conformation of human alpha 2-macroglobulin as revealed by differential scanning calorimetric analysis.
Differential scanning calorimetric analysis was used as a probe of the conformational alteration in human alpha 2-macroglobulin (AM) upon its complex formation with methylamine and with the protease, human plasmin. The slow electrophoretic form of AM displayed a single thermal transition, characterized by a temperature midpoint (Tm) of 65.8 +/- 0.3 degrees, a calorimetric enthalpy (delta Hc) of 2,550 +/- 150 kcal/mol and a van't Hoff enthalpy (delta Hvh) of 140 kcal/mol. In the presence of sufficient methylamine to irreversibly disrupt the four thiol ester bonds in AM, a single thermal transition was obtained, characterized by a Tm of 62.8 +/- 0.3 degrees, a delta Hc of 1,700 +/- 100 kcal/mol, and a delta Hvh of 169 kcal/mol. These data suggest that a major conformational alteration is produced in AM upon complex formation with methylamine. When plasmin interacts with AM, the resulting thermogram displays Tm values for AM of 68-69 degrees and 77 degrees, also suggestive of a large conformational alteration in AM. However, this latter alteration appears dissimilar to the change induced by methylamine.
D002152:Calorimetry, Differential Scanning; D005341:Fibrinolysin / Q000378:metabolism*; D006801:Humans; D008744:Methylamines / Q000494:pharmacology*; D011485:Protein Binding; D011487:Protein Conformation; D000511:alpha-Macroglobulins / Q000378:metabolism*
D008744:Methylamines; D000511:alpha-Macroglobulins; C027451:methylamine; D005341:Fibrinolysin