Linked Life Data

1396330

Source:http://linkedlifedata.com/resource/pubmed/id/1396330

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
4
pubmed:dateCreated
1992-11-13
pubmed:abstractText
Type I iodothyronine 5' deiodinase (5'DI) contains selenocysteine, encoded by a UGA codon, and this amino acid is essential for maximum catalytic efficiency in this enzyme. We recently showed that translation of UGA as selenocysteine in this protein requires a specific sequence of about 250 nucleotides in the 3' untranslated region of the messenger RNA. Translation of a 5'DI cysteine mutant does not require the 3' untranslated region. To examine both the efficiency of UGA codon recognition and the relative catalytic efficiency of selenocysteine vs. cysteine in 5'DI, we used bromoacetyl 125I-T3 labeling to quantitate transiently expressed selenocysteine (wild type) and cysteine containing type I iodothyronine deiodinases in transfected COS-7 and JEG-3 cell lines. Kinetic analyses of the same cell sonicates were performed to determine the apparent maximum velocity and Michaelis-Menten constant values for reverse T3 5' deiodination. COS-7 cells express the cysteine mutant protein at about 20-fold and JEG-3 cells about 400-fold higher levels than the selenoenzyme. However, in both cell types, the apparent catalytic constant values were at least 100-fold higher for the wild-type enzyme, compared with the cysteine mutant. These results indicate that cell lines differ markedly in their capacity to translate UGA-containing messenger RNAs. The much higher catalytic constant values for the selenium-containing enzyme illustrate the biochemical advantage of this element as compared with sulfur in the catalysis of iodothyronine deiodination.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
AIM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Oct
pubmed:issn
0013-7227
pubmed:author
pubmed:issnType
Print
pubmed:volume
131
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
1848-52
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
1992
pubmed:articleTitle
Substitution of cysteine for selenocysteine in type I iodothyronine deiodinase reduces the catalytic efficiency of the protein but enhances its translation.
pubmed:affiliation
Thyroid Division, Brigham and Women's Hospital, Boston, Massachusetts 02115.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, Non-U.S. Gov't