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Purification and characterization of a "half-molecule" alpha 2-macroglobulin from the southern grass frog: absence of binding to the mammalian alpha 2-macroglobulin receptor.

Publication ,  Journal Article
Feldman, SR; Pizzo, SV
Published in: Biochemistry
February 11, 1986

An alpha-macroglobulin (alpha 2M), which is a dimer consisting of two non-disulfide-bonded subunits, was identified and purified from frog plasma by Ni2+ chelate affinity chromatography. This frog "half-molecule" alpha-macroglobulin migrated as an alpha 2-globulin in cellulose-acetate electrophoresis rather than as the previously described frog alpha 1M, which exists as a tetramer formed by the noncovalent association of disulfide-bonded pairs. A molecular weight of approximately 380 000 was obtained by gel-filtration high-pressure liquid chromatography, and in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) the protein migrated as a single band of Mr approximately 180 000 before and after reduction. No evidence was obtained for association of this protein to a higher molecular weight species. After the preparation was heated, additional bands were obtained in SDS-PAGE with Mr approximately 60 000 and 12 000. The additional bands were not obtained after heating methylamine-treated preparations. The circular dichroic spectrum of frog alpha 2M exhibits negative ellipticity over the region 205-250 nm with a minimum at 216 nm. After reaction with proteinase, a decrease in the absolute mean residue rotation was obtained. Amino acid analysis demonstrated that frog alpha 2M and alpha 1M are similar in composition to avian and mammalian alpha-macroglobulins; however, there are sufficient differences in the composition of these two amphibian alpha-macroglobulins to support the conclusion that they are distinct proteins. Frog alpha 2M bound approximately 0.5 mol of trypsin/mol of inhibitor. This binding was abolished by pretreatment with methylamine.(ABSTRACT TRUNCATED AT 250 WORDS)

Duke Scholars

Published In

Biochemistry

DOI

ISSN

0006-2960

Publication Date

February 11, 1986

Volume

25

Issue

3

Start / End Page

721 / 727

Location

United States

Related Subject Headings

  • alpha-Macroglobulins
  • Species Specificity
  • Receptors, Immunologic
  • Rana pipiens
  • Protein Conformation
  • Molecular Weight
  • Models, Molecular
  • Macromolecular Substances
  • Low Density Lipoprotein Receptor-Related Protein-1
  • Kinetics
 
Journal cover image

Published In

Biochemistry

DOI

ISSN

0006-2960

Publication Date

February 11, 1986

Volume

25

Issue

3

Start / End Page

721 / 727

Location

United States

Related Subject Headings

  • alpha-Macroglobulins
  • Species Specificity
  • Receptors, Immunologic
  • Rana pipiens
  • Protein Conformation
  • Molecular Weight
  • Models, Molecular
  • Macromolecular Substances
  • Low Density Lipoprotein Receptor-Related Protein-1
  • Kinetics