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Effect of methylamine and plasmin on the conformation of human alpha 2-macroglobulin as revealed by differential scanning calorimetric analysis.

Authors
  • Cummings, H S
  • Pizzo, S V
  • Strickland, D K
  • Castellino, F J
Type
Published Article
Journal
Biophysical journal
Publication Date
Apr 01, 1984
Volume
45
Issue
4
Pages
721–724
Identifiers
PMID: 6202335
Source
Medline
License
Unknown

Abstract

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.

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