JBC, Vol. 250, Issue 18, 7294-7299, Sep, 1975
Elementary chain composition of guinea pig thyroglobulin
A. Haeberli, J. Bilstad, H. Edelhoch and J. E. Rall
Thyroglobulin obtained from guinea pigs was examined by Na
dodecyl-SO4-polyacrylamide gel electrophoresis after reduction and
alkylation. In contrast to thyroglobulin from other mammalian sources, only
three groups of polypeptide chains accounted for 95% or more of the
protein. Determinations of the molecular weights of these purified proteins
by equilibrium centrifugation in 6 M guanidine HCl gave values of 295,000
(species A), 210,000 (species B), and 110,000 (species C). Molecular
weights determined by gel filtration in 6 M guanidine HCl gave similar
results. Due to the large size of the polypeptides, satisfactory molecular
weights could not be obtained from Na dodecyl-SO4-polyacrylamide gel
electrophoresis. Amino acid analysis of the three species was similar to
that of whole thyroglobulin. Only slightly higher level of lysine and
histidine and a lower level of glutamic acid were seen in species C. The
iodine contents were found to range from 0.07 to 0.12 to 0.20% for species
A, B, and C, respectively.