SELENOCYSTEINE

Domain	Definition
Health	A naturally occurring amino acid in both eukaryotic and prokaryotic organisms. It is found in tRNAs and in the catalytic site of some enzymes. The genes for glutathione peroxidase and formate dehydrogenase contain the TGA codon, which codes for this amino acid. (references)
Source: compiled by the editor from various references; see credits.

Specialty Definition: Selenocysteine

Selenocysteine is an amino acid that is present in several enzymes (glutathione peroxidase, tetraiodothyronine 5' deiodinase, and formate dehydrogenase for example). Selenocysteine has a structure similar to cysteine, but with an atom of selenium taking the place of the usual sulfur. Proteins that include a selenocysteine residue are called selenoproteins.

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 appears soon after the UGA codon. In archaea and in eukaryotes, the SECIS element is in the 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.

Like the other amino acids used by cells, selenocysteine has a specialized tRNA. The primary and secondary structure of selenocysteine tRNA differ from those of standard tRNAs in several respects, most notably in having an 8-base pair acceptor stem, a long variable region arm, and substitutions at several well-conserved base positions.

Anagrams: SELENOCYSTEINE

Scrabble® Enable2K-Verified Anagrams
	Words within the letters "c-e-e-e-e-i-l-n-n-o-s-s-t-y"
	-4 letters: insolences, selections, sentiences.
	-5 letters: cysteines, cytosines, elections, enceintes, enlistees, eyestones, insolence, insolents, intensely, leniences, licensees, necessity, neotenies, nescients, nonstyles, seicentos, selectees, selection, selenites, senescent, sentences, sentience, sentinels, synclines, syntonies.
Source: compiled by the editor from various references; see credits. SCRABBLE® is a registered trademark. All intellectual property rights in and to the game are owned in the U.S.A and Canada by Hasbro Inc., and throughout the rest of the world by J.W. Spear & Sons Limited of Maidenhead, Berkshire, England, a subsidiary of Mattel Inc. Mattel and Spear are not affiliated with Hasbro.