AMINO-ACID-COMPOSITION AND MOLECULAR-WEIGHT OF BUFFALO THYROGLOBULIN

The amino acid composition of DEAE-cellulose purified buffalo thyroglobulin is similar to other mammalian thyroglobulins, and accounts for nearly 84% of the weight of the protein. The protein is rich in acidic amino acids, and its weight is approximately one-fifth of the protein weight. The protein has low amounts of histidine and methionine (1%). The amount of proline andl eucine are similar (7.5%), however, the content of proline is 2% higher than of other thyroglobulins, a value which might bear an impact on the secondary structure of the molecule. There are about 5 124 amino acid residues per mole of thyroglobulin. The number of half cystines, as determined by performic acid oxidation is 170, a value lower than other thyroglobulins. the molecular weight of buffalo thyroglobulin as analysed by Archibald's approach to sedimentation equalibrium is 685000, a value similar to other mammalian thyroglobulins.