Letter to the Editor

Gb, Wilson; Arnaúd, Philippe; Mt, Monsher; Hh, Fudenberg

doi:10.1203/00006450-197612000-00011

Pediatr Res

1976

DOI: 10.1203/00006450-197612000-00011

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Letter to the Editor

Wilson Gb

Philippe Arnaúd

Monsher Mt

et al.

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Cited by 5 publications

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“…Research on the interaction of a2M with proteinases has received a stimulus from the suggestion that a2M of people homozygous for the hereditary disease cystic fibrosis reacts abnormally (Shapira et al, 1977;Wilson & Fudenberg, 1976). Clearly it is of interest to understand in detail the structure of the a2M molecule, and to know how it is changed in course of reaction with a proteinase.…”

mentioning

confidence: 99%

The electrophoretically ‘slow’ and ‘fast’ forms of the α2-macroglobulin molecule

Barrett¹,

Brown²,

Sayers³

1979

Biochemical Journal

524

441

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alpha 2-Macroglobulin (alpha 2M) was isolated from human plasma by a four-step procedure: poly(ethylene glyco) fractionation, gel chromatography, euglobulin precipitation and immunoadsorption. No contaminants were detected in the final preparations by electrophoresis or immunoprecipitation. The protein ran as a single slow band in gel electrophoresis, and was designated 'S-alpha 2M'. S-alpha 2M bound about 2 mol of trypsin/mol. Treatment of S-alpha 2M with a proteinase or ammonium salts produced a form of the molecule more mobile in electrophoresis, and lacking proteinase-binding activity (F-alpha 2M). The electrophoretic mobility of the F-alpha 2M resulting from reaction with NH4+ salts was identical with that of proteinase complexes. We attribute the change in electrophoretic mobility of the alpha 2M to a conformation change, but there was no evidence of a change in pI or Strokes radius. Electrophoresis of S-alpha 2M in the presence of sodium dodecylsulphate gave results consistent with the view that the alpha 2M molecule is a tetramer of identical subunits, assembled as a non-covalent pair of disulphide-linked dimers. Some of the subunits seemed to be 'nicked' into two-thires-length and one-third-length chains, however. This was not apparent with F-alpha 2M produced by ammonium salts. F-alpha 2M produced by trypsin showed two new bands attributable to cleavage of the subunit polypeptide chain near the middle. Immunoassays of F-alpha 2M gave 'rockets' 12-29% lower than those with S-alpha 2M. The nature of the interactions between subunits in S-alpha 2M and F-alpha 2M was investigated by treating each form with glutaraldehyde before electrophoresis in the presence of sodium dodecyl sulphate. A much greater degree of cross-linking was observed with the F-alpha 2M, indicating that the subunits interact most closely in this form of the molecule. Exposure of S-alpha 2M to 3 M-urea or pH3 resulted in dissociation to the disulphide-bonded half-molecules; these did not show the proteinase-binding activity characteristic of the intact alpha 2M. F-alpha 2M was less easily dissociated than was S-alpha 2M. S-alpha 2M was readily dissociated to the quarter-subunits by mild reduction, with the formation of 3-4 new thiol groups per subunit. Inact reactive alpha 2M could then be regenerated in high yield by reoxidation of the subunits. F-alpha 2M formed by reaction with a proteinase or ammonium salts was not dissociated under the same conditions, although the interchain disulphide bonds were reduced. If the thiol groups of the quarter-subunits of S-alpha 2M were blocked by carboxymethylation, oxidative reassociation did not occur. Nevertheless treatment of these subunits with methylammonium salts or a proteinase caused the reassembly of half-molecules and intact (F-) tetramers. It is emphasized that F-alpha 2M does not have the properties of a denatured form of the protein...

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mentioning

confidence: 99%

The electrophoretically ‘slow’ and ‘fast’ forms of the α2-macroglobulin molecule

Barrett¹,

Brown²,

Sayers³

1979

Biochemical Journal

524

441

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Quantitative variation in cystic fibrosis-associated proteins in cystic fibrosis patients, carriers, and controls

et al. 1985

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Ciliary dyskinesia factors in cystic fibrosis and asthma

Wilson

Fudenberg

1977

Nature

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Letter to the Editor

Cited by 5 publications

References 4 publications

The electrophoretically ‘slow’ and ‘fast’ forms of the α2-macroglobulin molecule

The electrophoretically ‘slow’ and ‘fast’ forms of the α2-macroglobulin molecule

Quantitative variation in cystic fibrosis-associated proteins in cystic fibrosis patients, carriers, and controls

Ciliary dyskinesia factors in cystic fibrosis and asthma

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