Low molecular weight plasma proteins isolated from preparations of human immunoglobulin

Steven D. Carson, Barbara H. Bowman

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


Low molecular weight proteins co-purified with IgG constitute 0.22% of the total protein purified from human plasma by ion-exchange chromatography on DEAE-cellulose. We have found that these low molecular weight proteins were obtained free of immunoglobulin by ultrafiltration in 5 M guanidinium chloride. Electrophoresis and isoelectric focusing in polyacrylamide gels demonstrated that this fraction of low molecular weight proteins is remarkably heterogeneous. Chromatography of an Mr 6000 to 12 000 fraction on hydroxyapatite resolved fourteen discrete protein peaks. Three of the peaks contained proteins which appeared to be homogeneous on acid-urea polyacrylamide gels. Two of these proteins were similar in composition to B2 globulin and may represent degradation products of some larger protein. The third protein was found to have an amino-terminal sequence identical to C3a. This population of low molecular weight plasma proteins has previously been shown to contain the cystic fibrosis mucociliary inhibitor and is here shown to contain two proteins similar to B2 globulin, C3a and many proteins remaining to be characterized. The presence of these low molecular weight proteins in measurable concentrations may be insufficiently appreciated in studies using 'purified' immunoglobulins as biological or chemical probes.

Original languageEnglish (US)
Pages (from-to)23-34
Number of pages12
JournalBBA - Protein Structure
Issue number1
StatePublished - Jan 30 1981
Externally publishedYes


  • (Human plasma)
  • Cationic proteins
  • Immunoglobulin
  • Low molecular weight proteins

ASJC Scopus subject areas

  • General Medicine


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