Characterization of abnormal thyroglobulin in a transplantable rat thyroid tumor

The solube iodoproteins in a transplantable rat throid tumor (Wollman Line 1-8) were studied after in vivo labeling with 125 I and were partially purified by affinity chromatography on anti-thyroglobulin-AGAROSE. A major fraction ('Peak A') was excluded from gels of large pore size, but had a low sedimentation rate (approximately8S) and did not appear to contain aggregates. It had a high density (approximately1.4) which was possibly due to a high content of carbohydrate, since treatment with a crude glycosidase mixture lowered the density to approximately1.3. A second fraction ('Peak B') had a similar sedimentation coefficient (6-9S) but penetrated the same gels and had a lower density (approximately 1.3). Both proteins formed soluble complexes with antibodies against normal rat thyroglobulin, and had other properties somewhat similar to those of thyroglobulin. After hydrolysis, mono- and diiodotyrosine were the only iodoamino acids liberated. These iodoproteins appears to represent abnormal forms of thyroglobulin synthesized by the tumor.