Investigations of the structural function of the J chain in human immunoglobulin M

Abstract

Human IgM molecules were treated with Na(2)SO(3) or mercaptoethylamine in concentrations ranging from 2 to 14mm or 2 to 22mm respectively. The dissociation of IgM to IgM(s) varied from 0% to 100%. At the intermediate concentrations of either reagent the amount of freed J chains was less than expected. In an attempt to find an explanation for this, IgM was partially dissociated to IgM(s) with mercaptoethylamine. The IgM(s) isolated by gel filtration was divided according to the ascending and descending portions of the elution curve. These portions were treated with 24mm-mercaptoethylamine and analysed for the presence of J chains. Only the ascending portion contained free J chains. Thus, after mild reduction where not all the IgM molecules are dissociated to IgM(s), some J chains remain covalently attached to some IgM(s) molecules although most of the J chains are freed. It was concluded that the J chain could serve as a ;hitch' for IgM(s) molecules forming intact IgM.

Production of a Noncovalently Bonded Pentamer of Immunoglobulin M: Relationship to J Chain

“…This is also supported by the observation that 10 of the 12 half-cystines in J chain must be reduced before appreciable amounts were released from IgM (3). The release of J chain when the intersubunit bonds are selectivelv cleaved, as found in this study as well as in a recent report (12), is consistent with this thesis. These results would also suggest that once the interchain bonds are cleaved, the noncovalent interactions between J and IgMr, are not of sufficient strength to hold them together during chromatography on Sephadex G-200 in aqueous buffers.…”

“…The IgIM was reduced according to Morris and Inman (7) at a protein concentration of 5 mg/ml, with 10-25 mM mercaptoethylamine for 1 hr at 300, followed by alkylation with [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] A partial specific volume of 0.717 was assumed in accordance with previously reported values for IgM (11).…”

The incorporation of J chain into reassembled human immunoglobulin M

“…The molecular weight of J chain from IgA was reported to be about 15000 (O'Daly & Cebra, 1971;Schrohenloher et al, 1973). The molecular weight of the J chain from IgM (Gra) was shown also to be about 15000 (Ricardo et al, 1973). The polypeptide, however, existed in borate-saline solution as a dimer of 30000.…”

The molecular weight of J chains derived from human immunoglobulin M

“…IgM was treated with 0.25M-Na2SO3 as described by Edelman & Marchalonis (1967). The J-chain protein sometimes was isolated by electrophoresis of the sulphonated IgM on slabs of polyacrylamide gel (Ricardo & Inman, 1973). Alternatively, sulphonated IgM was subjected to polyacrylamide-gel electrophoresis and one gel was stained with Coomassie Blue (Ricardo & Inman, 1973).…”

“…The J-chain protein sometimes was isolated by electrophoresis of the sulphonated IgM on slabs of polyacrylamide gel (Ricardo & Inman, 1973). Alternatively, sulphonated IgM was subjected to polyacrylamide-gel electrophoresis and one gel was stained with Coomassie Blue (Ricardo & Inman, 1973). The stained gel was used as a marker for the J-chain position, and the corresponding regions were cut out of the unstained gels.…”