Abstract
We have examined the polypeptide chain composition of membrane-bound and detergent-solubilized Ia antigens using the chemical cross-linking reagent dimethyl 3,3′-dithiobispropionimidate (DTBP). Products of the I-E/C subregion of the major histocompatibility complex, which were solubilized from spleen cells with the detergent NP-40 and partially purified by affinity chromatography on lentil lectin-agarose, could be almost completely cross-linked by DTBP. Thus, the characteristic 33,000 m.w. (α) and 28,000 (β) polypeptide chains seen on sodium dodecylsulfate polyacrylamide gels disappeared and a major new species of 60,000 m.w. appeared after cross-linking. When isolated and reduced with 2-mercaptoethanol, the 60,000 m.w. peak was found to be comprised of α and β chains. Similar results were obtained when I-E/C, as well as I-A, α and β chains were cross-linked on the cell surface. These data demonstrate that the α and β chains of the Ia antigens exist primarily in the form of a dimer both in detergent solution and in situ.
Footnotes
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↵1 This work was supported in part by National Institutes of Health Grant 1-RO1-AI-13782 and Grant IM-131 from the American Cancer Society.
- Received March 8, 1979.
- Accepted May 17, 1979.
- Copyright © 1979 by The American Association of Immunologists, Inc.
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