ISSN:
1432-072X
Keywords:
Key wordsEscherichia coli
;
Selenoproteins
;
Selenocysteine
;
Selenomethionine
;
Monoselenophosphate synthetase
;
Cysteine biosynthesis
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract The path of unspecific selenium incorporation into proteins was studied in Escherichia coli mutants blocked in the biosynthesis of cysteine and methionine or altered in its regulation. Selenium incorporation required all enzymatic steps of cysteine biosynthesis except sulfite reduction, indicating that intracellular reduction of selenite occurs nonenzymatically. Cysteine (but not methionine) supplementation prevented unspecific incorporation of selenium by repressing cysteine biosynthesis. On the other hand, when the biosynthesis of cysteine was derepressed in regulatory mutants, selenium was incorporated to high levels. These findings and the fact that methionine auxotrophic strains still displayed unspecific incorporation show that selenium incorporation into proteins in E. coli occurs mainly as selenocysteine. These findings also provide information on the labeling conditions for incorporating 75Se only and specifically into selenoproteins.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s002030050517
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