Isolation procedures for thyroglobulin: effects of phenylmethanesulfonyl fluoride and freezing

The presence of fast-migrating, low-molecular weight components in normal rat thyroglobulin, iodine-poor rat thyroglobulin and normal bovine thyroglobulin was investigated by polyacrylamide gel electrophoresis in sodium dodecyl sulfate. When normal and iodine-poor rat thyroglobulin were extracted in the presence of phenylmethanesulfonyl fluoride, a serine protease inhibitor, very few components migrating faster than the 12S half-molecule were found. In normal bovine thyroglobulin no effect of the protease inhibitor on the formation of fast-moving components was found; however, prior freezing of the glands greatly influenced the presence of these components. Thyroglobulin obtained from bovine glands without any prior freezing, contained no noncovalently-bound band migrating faster than 12S.