title: Thio reduction of human   2 -macroglobulin. The subunit structure.
abstract: 1. Human alpha(2)-macroglobulin was prepared from a fraction obtained during the large-scale separation of normal human plasma proteins for clinical use. 2. Sedimentation-equilibrium measurements indicated a molecular weight of 725000. A value of 18.1S was obtained for s(0) (20,w). 3. The dissociation that occurs in the pH range 4.5-2.5 and in the region of neutrality in urea-containing solutions is consistent with a dimeric structure of the molecule. 4. The effects of the thiol reagents mercaptoethanol, mercaptoethylamine and N-acetylcysteine were investigated over a range of experimental conditions. Distinct components having sedimentation coefficients of 15, 12 and 8.5S were identified. 5. Conditions were found under which limited reduction with thiol liberated a subunit with a molecular weight approximately one-quarter of that of the intact molecule. This subunit retains the serological specificity of the whole molecule.
mesh_terms: D000111:Acetylcysteine; D001798:Blood Proteins / Q000302:isolation & purification; D055598:Chemical Phenomena; D002621:Chemistry; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008259:Macroglobulins; D008623:Mercaptoethanol; D008624:Mercaptoethylamines; D008970:Molecular Weight; D009905:Optical Rotatory Dispersion; D010084:Oxidation-Reduction; D014508:Urea
chemical_list: D001798:Blood Proteins; D008259:Macroglobulins; D008624:Mercaptoethylamines; D008623:Mercaptoethanol; D014508:Urea; D000111:Acetylcysteine