Purification and some properties of microsome-bound thyroglobulins

Area of Science:

• Biochemistry
• Endocrinology
• Molecular Biology

Background:

• Thyroglobulin is a key protein in thyroid hormone synthesis.
• Microsomal fractions contain proteins involved in thyroid hormone production.

Purpose of the Study:

• To identify and characterize proteins in hog thyroid microsomal fractions that react with anti-thyroglobulin antiserum.
• To investigate the relationship between these proteins and thyroglobulin in thyroid hormone production.

Main Methods:

• Ammonium sulfate precipitation
• Sucrose density gradient centrifugation
• Polyacrylamide gel electrophoresis
• Amino acid composition analysis
• Carbohydrate content analysis (mannose, galactose, fucose, sialic acid)
• Iodine content determination
• Antigenic activity assay
• Sedimentation coefficient measurement

Main Results:

• Two thyroglobulin-related proteins, S-mb thyroglobulin and F-mb thyroglobulin, were purified from hog thyroid microsomal fractions.
• These proteins exhibited quantitative differences in sialic acid, iodine, galactose, and fucose content compared to thyroglobulin.
• S-mb thyroglobulin lacked sialic acid and iodine, while F-mb thyroglobulin had reduced levels of both.
• Both S-mb and F-mb thyroglobulin showed qualitatively similar but quantitatively lower antigenic activity than thyroglobulin.
• Sedimentation coefficients indicated S-mb and F-mb thyroglobulin are smaller than thyroglobulin.

Conclusions:

• S-mb thyroglobulin and F-mb thyroglobulin are sequentially modified forms of thyroglobulin.
• These modified proteins are likely intermediates in the thyroid hormone production pathway.