Abstract
The intact proteins and Fab and Fc fragments of normal γG and myeloma proteins of the four γG subclasses were studied for their susceptibility to heat aggregation. It was found that in the case of normal γG and myeloma proteins of the two major subclasses, γG1 and γG2, aggregation of the intact protein correlated with aggregation of the Fab fragment, whereas the Fc fragments of these proteins did not aggregate appreciably. In the case of the two minor subclasses, γG3 and γG4, the Fc fragment was also a contributing factor in the formation of heat aggregates. Aggregation could be partially reversed (54% to 73%) by treatment with 8 M urea, indicating that both disulfide bonds and non-covalent interactions were responsible for the formation of the aggregates. It was also found that heat aggregation of γG1 protein leads to a conformational change in the Fab which renders it extremely susceptible to proteolysis. The significance of these findings with respect to the mechanism by which aggregation results in the enhanced biologic activity of the Fc fragment is discussed.
Footnotes
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↵1 This is publication 391 from the Department of Experimental Pathology, Scripps Clinic and Research Foundation, La Jolla, California. This investigation was supported by United States Public Health Service Grant A1-07007, Atomic Energy Commission Contract AT(04-3)-410, American Heart Association Grant 67–795 and United States Public Health Service Training Grant 5T1 GM 683.
- Received January 6, 1970.
- Copyright © 1970 by The American Association of Immunologists, Inc.
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