L-selenocysteineSeC 3 NO 2 H 7 selenoamino acid
Selenocysteine (symbol Sec or U, in older publications also as Se-Cys) is the 21st proteinogenic amino acid.wikipedia
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Thyroxine 5-deiodinase

DIO3Dlk1-Dio3 geneType III iodothyronine deiodinase
This protein contains a selenocysteine (Sec) residue, which is essential for efficient enzyme activity.

John F. Atkins

Proteinogenic amino acids that are not part of the genetic code, e.g. the 21st amino acid selenocysteine and the 22nd amino acid pyrrolysine are also subjects of Recoding.

Sulfur assimilation

assimilation of sulfurassimilatory sulfate reduction
Glutathione is directly involved in the reduction and assimilation of selenite into selenocysteine.


This gene encodes a selenoprotein containing multiple selenocysteine (Sec) residues, which are encoded by the UGA codon that normally signals translation termination.

Organoselenium chemistry

organoselenium compoundallylic oxidationselenoxide
Selenocysteine, called the twenty-first amino acid, is essential for ribosome-directed protein synthesis in some organisms.


molybdenum pterin
Although a tungsten-containing xanthine dehydrogenase from bacteria has been found to contain tungsten-molybdopterin and also non-protein-bound selenium (thus removing the possibility of selenium in selenocysteine or selenomethionine form), a tungsten-selenium molybdopterin complex has not been definitively described.


Glutathione peroxidase 4
In selenoproteins, the 21st amino acid selenocysteine is inserted in the nascent polypeptide chain during the process of translational recoding of the UGA stop codon.

Translation (biology)

translationtranslatedprotein translation
This approach may not give the correct amino acid composition of the protein, in particular if unconventional amino acids such as selenocysteine are incorporated into the protein, which is coded for by a conventional stop codon in combination with a downstream hairpin (SElenoCysteine Insertion Sequence, or SECIS).

Earl Reece Stadtman

Earl R. StadtmanEarl StadtmanE. R. Stadtman
He was the husband of Thressa Stadtman, who discovered selenocysteine.

Sulfite reductase

dissimilatory sulfite reductasesulfite reductase (nadph)sulfite-
This enzyme participates in selenoamino acid metabolism and sulfur assimilation.


Selenoprotein T contains a selenocysteine (Sec) residue at its active site.

Chargaff's rules

Chargaff's ruletwo rulesAT/GC
(There are two uncommon amino acids—selenocysteine and pyrrolysine—found in a limited number of proteins and encoded by the stop codons—TGA and TAG respectively.) The mismatch between the number of codons and amino acids allows several codons to code for a single amino acid - such codons normally differ only at the third codon base position.

Olavius algarvensis

One of the Deltaproteobacteria symbionts, called "Delta-1", is able to produce numerous seleno- and pyrroproteins, which contain the amino acids selenocysteine and pyrrolysine that are sometimes called the 21st and 22nd proteinogenic amino acids.

Krishna Chatterjee

He has shown how deficiency of human selenocysteine-containing proteins causes a multisystem disease, including disordered thyroid hormone metabolism.

Nickel compounds

Some hydrogenase enzymes contain a nickel-iron cluster as an active site in which the nickel atom is held in place by cysteine or selenocysteine.



Selenophosphate synthetase 1

selenophosphateselenophosphate synthetaseSEPHS1
Selenophosphate is the selenium donor used to synthesize selenocysteine, which is co-translationally incorporated into selenoproteins at in-frame UGA codons.


The mammalian version of the protein thioredoxin reductase contains a selenocysteine residue which forms a thioselenide (analogous to a disulfide) upon oxidation.

Period 4 element

fourth periodPeriod 44
Selenium is a component of the noncanonical amino acid, selenocysteine; proteins which contain selenocysteine are known as selenoproteins.