7S IMMUNOGLOBULINS OF A MONOTREME, ECHIDNA TACHYGLOSSUS-ACULEATUS - 2 DISTINCT ISOTYPES WHICH BIND A-PROTEIN OF STAPHYLOCOCCUS-AUREUS

  • 1 January 1978
    • journal article
    • research article
    • Vol. 34  (1) , 97-103
Abstract
The 7S immunoglobulins [Ig] of a monotreme mammal, echidna T. aculeatus, bind to S. aureus A protein coupled to an insoluble matrix. This binding supports the homology between the previously described echidna IgG and IgG molecules of higher mammals and provides a rapid, simple method for the isolation of this protein from echidna serum. Another echidna 7S immunoglobulin became bound to protein A-Sepharose. The major protein A-binding Ig has a slow electrophoretic mobility and possesses a H chain comparable in mass to typical mammalian .gamma. chains (52,000 daltons). The designation IgG2 is suggested for this Ig. The minor protein A-binding Ig is electrophoretically faster than IgG2 and can be resolved from the former by gradient elution from DEAE-Biogel. The nomenclature is suggested IgG1 for this molecule, although the possibility that it might represent another main class such as IgA cannot be discounted. The .gamma.1 H chain is distinguishable from the .gamma.2 chain on polyacrylamide gel electrophoresis in sodium dodecylsulfate containing buffers. The .gamma.1 chain possesses a nominal mass of 61,000 daltons. The intact molecule has an apparent mass of 177,000 Daltons and comprises 2 pairs of L and H chains.