Polypeptide chain composition of thyroglobulin.

It is known that thyroglobulin can be dissociated into a component which appears to be a half molecule (12 S) of the undissociated molecule (19 S). In the present work, these two molecular species were isolated with a high degree of purity by preparative gel electrophoresis in sodium dodecyl sulfate and were individually reduced. The reduction pattern of the 12 S form displayed only two closely migrating bands, both having an apparent Mr near 330 000, whereas the undissociated (covalently linked) 19 S form showed a complex pattern consisting of, besides the 330 000 doublet, nonreducible material and several faster bands, resembling the pattern of the unfractionated protein. The origin of the faster-moving peptides is not known. These results have been obtained with both hog and rat thyroglobulin.