Document Detail

Similar hormone-rich peptides from thyroglobulins of five vertebrate classes.
MedLine Citation:
PMID:  6606572     Owner:  NLM     Status:  MEDLINE    
Thyroglobulins (Tgs) were purified from five species (rat, chicken, turtle, frog, and goldfish), each representing a different vertebrate class. On reduction with mercaptoethanol, each Tg produced five major iodopeptides, designated A-E, with ranges of estimated molecular mass, in kilodaltons (K), as follows: A, more than 300K; B, 210-280K; C, 30-42K; D, 19-28K; and E, 10-23K. Of these, the two smallest, D and E, had 40-80% of their iodine as iodothyronine, compared with 15-20% for the parent Tgs. They contained 25-63% of Tg's total iodothyronines but only a few percent of its peptide material. Calculations from amino acid analyses and iodine contents showed approximately 1 mol each of D and E/mol 660,000 dalton Tg. In comparisons of amino acid compositions by cluster analysis, iodopeptides D and E resembled each other and their counterparts in other species more than they resembled their parent Tgs. Also, the Tgs from different species were more similar to each other and to iodopeptides D and E than to nonthyroidal proteins randomly selected from the literature. We injected 125I into rats and turtles, and compared its distribution among the iodopeptides to that of 127I. These dual isotope experiments showed that as Tg was iodinated in vivo, iodopeptide B decreased both in molecular size and in its share of Tg's iodine, while the sum of iodopeptides D and E increased, indicating that B may be the precursor of D and E. In vivo iodination of rat Tg with 125I for different periods of time suggested that iodopeptide E and its iodothyronines are derived from a larger portion of the Tg molecule, perhaps iodopeptide B. The amount of 125I in iodopeptide D also increased with time. We conclude that these two discrete hormone-rich peptide fractions of small molecular weight are a consistent feature of Tg's structure throughout the vertebrate classes. Both are probably derived from a larger iodopeptide fraction (iodopeptide B) during the course of Tg maturation and iodination. Their conservation during evolution indicates an important role for them in thyroid hormone biosynthesis.
P S Kim; J T Dunn; D L Kaiser
Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Endocrinology     Volume:  114     ISSN:  0013-7227     ISO Abbreviation:  Endocrinology     Publication Date:  1984 Feb 
Date Detail:
Created Date:  1984-02-24     Completed Date:  1984-02-24     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  0375040     Medline TA:  Endocrinology     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  369-74     Citation Subset:  AIM; IM    
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MeSH Terms
Iodine Radioisotopes / diagnostic use
Molecular Weight
Peptides / isolation & purification*
Rana pipiens
Rats, Inbred Strains
Species Specificity
Thyroglobulin / isolation & purification*
Grant Support
Reg. No./Substance:
0/Iodine Radioisotopes; 0/Peptides; 9010-34-8/Thyroglobulin

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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