 Space-filling model of L-selenocysteine Selenocysteine is an amino acid that is present in several enzymes (for example glutathione peroxidases, tetraiodothyronine 5' deiodinases, thioredoxin reductases, formate dehydrogenases, glycine reductases and some hydrogenases). Selenocysteine has a structure similar to cysteine, but with an atom of selenium taking the place of the usual sulfur. Proteins that contains one or more selenocysteine residues are called selenoproteins. Image File history File links Size of this preview: 711 × 600 pixel Image in higher resolution (1100 × 928 pixel, file size: 22 KB, MIME type: image/png) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Amino acid Selenocysteine...
Image File history File links Size of this preview: 711 × 600 pixel Image in higher resolution (1100 × 928 pixel, file size: 22 KB, MIME type: image/png) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Amino acid Selenocysteine...
A skeletal formula is a three-dimensional model of the molecule that demonstrates the molecular shape, including bond angles. ...
Image File history File links Download high-resolution version (1100x935, 236 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Amino acid Selenocysteine ...
Image File history File links Download high-resolution version (1100x935, 236 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Amino acid Selenocysteine ...
This is a calotte model of cyclohexane. ...
Phenylalanine is one of the standard amino acids. ...
Ribbon diagram of the enzyme TIM, surrounded by the space-filling model of the protein. ...
Glutathione peroxidase (PDB 1GP1, EC 1. ...
Glutathione peroxidase is an protein ...
Thioredoxin Reductase (TR, TrxR) are the only known enzymes to reduce thioredoxin (Trx). ...
A hydrogenase is an enzyme that catalyses the reversible oxidation of molecular hydrogen (H2). ...
Cysteine is a naturally occurring, sulfur-containing amino acid that is found in most proteins, although only in small quantities. ...
Se redirects here. ...
General Name, Symbol, Number sulfur, S, 16 Chemical series nonmetals Group, Period, Block 16, 3, p Appearance lemon yellow Standard atomic weight 32. ...
A selenoprotein is any protein that includes a selenocysteine residue. ...
Unlike other amino acids present in biological proteins, however, it is not coded for directly in the genetic code. Selenocysteine is encoded in a special way by a UGA codon, which is normally a stop codon. The UGA codon is made to encode selenocysteine by the presence of a SECIS element (SElenoCysteine Insertion Sequence) in the mRNA. The SECIS element is defined by characteristic nucleotide sequences and secondary structure base-pairing patterns. In eubacteria, the SECIS element is located immediately following the UGA codon within the reading frame for the selenoprotein. In archaea and in eukaryotes, the SECIS element is in the 3' untranslated region (3' UTR) of the mRNA, and can direct multiple UGA codons to encode selenocysteine residues. When cells are grown in the absence of selenium, translation of selenoproteins terminates at the UGA codon, resulting in a truncated, nonfunctional enzyme. A representation of the 3D structure of myoglobin, showing coloured alpha helices. ...
A series of codons in a short RNA molecule. ...
RNA codons. ...
In biology, the SECIS element (SECIS: selenocysteine insertion sequence) is a structural motif (pattern of nucleotides) that directs the cell to translate UGA codons as selenocysteines. ...
The interaction of mRNA in a eukaryote cell. ...
Subgroups Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria (singular: bacterium) are microscopic, unicellular organisms. ...
Phyla / Classes Phylum Crenarchaeota Phylum Euryarchaeota Halobacteria Methanobacteria Methanococci Methanopyri Archaeoglobi Thermoplasmata Thermococci Phylum Korarchaeota Phylum Nanoarchaeota Archaea (; from Greek αÏχαία, ancient ones; singular Archaeum, Archaean, or Archaeon), also called Archaebacteria (), is a major division of living organisms. ...
Kingdoms Animalia - Animals Fungi Plantae - Plants Protista Alternative Phylogeny Unikonta Opisthokonta Amoebozoa Bikonta Apusozoa Cabozoa Rhizaria Excavata Corticata Archaeplastida Chromalveolata Animals, plants, fungi, and protists are eukaryotes (IPA: ), organisms with a complex cell or cells, where the genetic material is organized into a membrane-bound nucleus or nuclei. ...
In genetics, the 3 UTR (read as 3 prime untranslated region) is a particular section of messenger RNA (mRNA). ...
Like the other amino acids used by cells, selenocysteine has a specialized tRNA. The primary and secondary structure of selenocysteine tRNA, tRNA(Sec), differ from those of standard tRNAs in several respects, most notably in having an 8-base (bacteria) or 9-base (eukaryotes) pair acceptor stem, a long variable region arm, and substitutions at several well-conserved base positions. The selenocysteine tRNAs are initially charged with serine by seryl-tRNA ligase, but the resulting Ser-tRNA(Sec) is not used for translation because it is not recognised by the normal translation factor (EF-Tu in bacteria, EF1-alpha in eukaryotes). Rather, the tRNA-bound seryl residue is converted to a selenocysteyl-residue by the pyridoxal phosphate-containing enzyme selenocysteine synthase. Finally, the resulting Sec-tRNA(Sec) is specifically bound to an alternative translational elongation factor (SelB or mSelB) which delivers it in a targeted manner to the ribosomes translating mRNAs for selenoproteins. The specificity of this delivery mechanism is brought about by the presence of an extra protein domain (in bacterial SelB) or an extra subunit (SBP-2 for eukaryotic mSelB) which bind to the corresponding RNA secondary structures formed by the SecIS elements in selenoprotein mRNAs. The SecIS elements of bacterial selenoproteins (as far as analysed) are located within the coding sequences immediately following the UGA codons for selenocysteine, those of Eukarya and Archaea are located in the 3' UTR of the respective mRNAs. In addition, at least one case has been described for an archaeal selenoprotein mRNA containing its SecIS in the 5' UTR. Transfer RNA (abbreviated tRNA) is a small RNA chain (74-93 nucleotides) that transfers a specific amino acid to a growing polypeptide chain at the ribosomal site of protein synthesis during translation. ...
Pyridoxal-phosphate (PLP, pyridoxal-5-phosphate) is a cofactor of many enzymatic reactions. ...
In eukaryotic genetics, the 5 UTR (read as 5 prime UnTranslated Region) is a particular section of messenger RNA (mRNA). ...
The joint nomenclature committee of the IUPAC/IUBMB has officially recommended the three-letter symbol Sec and the one-letter symbol U for selenocysteine. The International Union of Pure and Applied Chemistry (IUPAC) is an international non-governmental organization devoted to the advancement of chemistry. ...
The International Union of Biochemistry and Molecular Biology (IUBMB). ...
See also
Sodium selenite, Na2SeO3, is a selenium compound. ...
Pyrrolysine is a naturally-occurring genetically-coded amino acid. ...
External links - IUPAC/IUBMB Recommendation
- Links to external chemical sources
- F. Zinoni, et al.; Nucleotide sequence and expression of the selenocysteine-containing polypeptide of format dehydrogenase (formate-hydrogen-lyaselinked) from Escherichia coli [1] [2]
- F. Zinoni, et al.; Cotranslational Insertion of Selenocysteine into Formate Dehydrgoenase from Escherichia coli Directed by a UGA Codon [3]
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