Cadmium binding to human α2-macroglobulin

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Abstract

α2-Macroglobulin (α2M) is one of the major cadmium-binding proteins of human plasma. As determined with equilibrium dialysis, α2M bound 4.6 (±0.7) mol Cd2+ per mol protein with an apparent dissociation constant of (9.6 (±5.0))·10-7M. Methylamine-modified α2M (α2M-Me) had a similar affinity for Cd2+ (Kd,app = 5.3·10-7M, but fewer binding sites. Cadmium produced a small increase in the amidolytic activity of trypsin in the presence of α2M and soybean trypsin inhibitor. Using the binding parameters determined from the equilibrium dialysis studies, the Cd2+ concentration which produced a half-maximal increase in amidolytic activity corresponded to saturation of all Cd2+-binding sites in one-half of the α2M molecules. From these results, a model is proposed in which one Cd2+-binding site is present in each of the four polypeptide chains which compose α2M.

Original languageEnglish (US)
Pages (from-to)370-374
Number of pages5
JournalBiochimica et Biophysica Acta (BBA)/Protein Structure and Molecular
Volume791
Issue number3
DOIs
StatePublished - Dec 21 1984

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Keywords

  • (Human)
  • Cd binding
  • Equilibrium binding
  • α-Macroglobulin

ASJC Scopus subject areas

  • Biophysics
  • Structural Biology
  • Biochemistry
  • Molecular Biology

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