Studies on the Catabolism of γG Subunits and Chains

Summary

The catabolism of I¹³¹ labeled H- and L-chain of RGG and HGG, Bence Jones protein and H-chain protein was studied in rabbits. Evidence is presented that the molecular structure responsible for the persistence in the circulation of γG is localized in the H-chain.

1. 1. The H-chain was slowly eliminated from the circulation similar to reduced and alkylated γG.

2. 2. The H-chain protein, obtained from patients with H-chain disease, was eliminated from the circulation with a half-life not significantly different from that of HGG. Two populations of H-chain protein with different electrophoretic mobilities were separated by DEAE-cellulose chromatography. Both populations were catabolized at the same rate. The rabbits did not excrete the H-chain protein in the urine.

3. 3. The L-chain and the Bence Jones protein were very rapidly eliminated from the circulation. A significant amount of the L-chain obtained from RGG but not from HGG was excreted in the urine as protein bound radioactivity.

Sialic acid was shown not to be an important part of the structure necessary for the persistence in the circulation of γG. Removal of sialic acid did not change the rate of elimination of HGG, HGG papain Fc fragment and an H-chain protein preparation with a low sialic acid content. In contrast, a large portion of the H-chain protein preparations with a high sialic acid content was rapidly eliminated and catabolized after removal of sialic acid.