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Topic: Selenocysteine

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SECIS element

Pyrrolysine

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Amino acid

Homocysteine

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Ricin

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The Yellow Book

	Selenocysteine - Wikipedia, the free encyclopedia
		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 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.
	en.wikipedia.org /wiki/Selenocysteine (466 words)

	[No title]
		Selenocysteine is very similar to the amino acid cysteine, the sulfur in cysteine has been changed to selenium.
		The elucidation of how selenocysteine is incorporated into protein has altered the understanding of the genetic code, as the code is now expanded to include selenocysteine as the twenty-first naturally occurring amino acid incorporated into proteins.
		The biosynthesis of selenocysteine that is incorporated into a protein in response to the UGA codon is distinctive from the other amino acids in the genetic code in that its synthesis always occurs on its tRNA.
	starklab.slu.edu /Coulter/genetics/CMG/selenocysteine.doc (3494 words)

	SECIS[ndash]SBP2 interactions dictate selenocysteine incorporation efficiency and selenoprotein hierarchy
		Decoding of UGA as selenocysteine occurs in eubacteria, archaea and eukarya.
		In Escherichia coli, the SECIS elements reside immediately downstream of each of the selenocysteine codons, and their positions are tightly constrained—movement of the stem upstream or downstream by as little as three nucleotides reduces or abolishes incorporation (Heider et al., 1992).
		Tujebajeva RM, Copeland PR, Xu XM, Carlson BA, Harney JW, Driscoll DM, Hatfield DL and Berry MJ (2000) Decoding apparatus for eukaryotic selenocysteine insertion.
	www.nature.com /emboj/journal/v19/n24/full/7593501a.html (6663 words)

	Selenocysteine tRNA Identification (Site not responding. Last check: 2007-11-07)
		The primary and secondary structure of selenocysteine tRNAs differ from canonical tRNAs in several respects, most notably an eight base pair acceptor stem, a long variable region arm, and substitutions at several well-conserved base positions.
		Pavesi et al., 1994] for identifying eukaryotic selenocysteine tRNAs (based on a B box score with a value between -2.2 and -3.6, and the motif GGTC(C/T)G(G/T)GGT appearing 36 nucleotides upstream of the B box).
		To similarly identify prokaryotic selenocysteine tRNAs, a subroutine was added to EufindtRNA which detects tRNAs with B box scores between -2.2 and -4.9, and a conserved sequence motif found in the anticodon loop of all known prokaryotic selenocysteine tRNAs (anticodon in bold): GG(A/T)(C/T)TTCAAA(A/T)CC.
	lowelab.ucsc.edu /~lowe/thesis/node22.html (344 words)

	Selenocysteine codons decrease polysome association on endogenous selenoprotein mRNAs -- Martin GW and Berry 6 (2): 121 ...
		Selenocysteine codons decrease polysome association on endogenous selenoprotein mRNAs -- Martin GW and Berry 6 (2): 121 -- Genes to Cells
		BACKGROUND: Selenocysteine incorporation has been reported to be inefficient in all systems studied, including Escherichia coli, baculovirus-insect cell systems, rabbit reticulocyte in vitro translation systems, transiently transfected mammalian cells, and intact animals.
		Nonetheless, full-length selenoproteins containing up to 17 selenocysteine residues are produced in animals, indicating that the efficiency observed in manipulated systems might not accurately reflect the true efficiency of this process in nature.
	www.genestocellsonline.org /cgi/content/abstract/6/2/121 (388 words)

	Selenocysteine tRNA Detection (Site not responding. Last check: 2007-11-07)
		The failure of the specialized routines may have been due in part to the fact that this is the first and only archaebacterial selenocysteine tRNA available to date.
		For the remaining non-archaeal selenocysteine tRNAs, use of the specialized models boosts covariance model scores from the 20-40 bit range to 45-72 bits.
		A search of the non-redundant database (nrdb) maintained at NCBI revealed no new selenocysteine tRNAs from species for which there was no previously noted sequence.
	lowelab.ucsc.edu /~lowe/thesis/node30.html (160 words)

	ARS \| Publication request: The Tga Stop Codon and the Phylogeny of the Selenocysteine Pathway
		We found that TGA is used in special context that is not directly related to the use of selenocysteine.
		We also found that the evolution of the selenocysteine usage indicates that it was an ancient trait that was probably common to all bacteria at one time and was lost by many modern species.
		In Pseudomonas aeruginosa, which also has the selenocysteine pathway, 78% of stop codons were found to be TGA of which 11.9% overlapped by 4 bases with the downstream gene.
	ars.usda.gov /research/publications/publications.htm?seq_no_115=149487 (581 words)

	selB - Selenocysteine-specific elongation factor (Site not responding. Last check: 2007-11-07)
		All the selB suppressor mutations isolated were clustered in a region corresponding to 28 amino acids in the SelB C-terminal subdomain 4b.
		It was found to be dependent on the positive control exerted by the fdhA, B and C genes, possibly involved in selenium incorporation, and by an hydB gene affecting the formate hydrogenlyase pathway.
		The function of selA, selB, and selC from E. acidaminophilum was investigated by complementation of the respective E. coli deletion mutant strains and determined as the benzyl viologen-dependent formate dehydrogenase activity in these strains after anaerobic growth in the presence of formate.
	www.pdg.cnb.uam.es /UniPub/iHOP/gg/171183.html (541 words)

	Overproduction of selenocysteine tRNA in Chinese hamster ovary cells following transfection of the mouse tRNA([Ser]Sec) ...
		Selenocysteine insertion during selenoprotein biosynthesis begins with the aminoacylation of selenocysteine tRNA([Ser]Sec) with serine, the conversion of the serine moiety to selenocysteine, and the recognition of specific UGA codons within the mRNA.
		Selenocysteine tRNA([Ser]Sec) exists as two major forms, differing by methylation of the ribose portion of the nucleotide at the wobble position of the anticodon.
		The levels of selenocysteine tRNA([Ser]Sec) in transfectants increased proportionally to the number of stably integrated copies of the tRNA([Ser]Sec) gene.
	www.egeinfonet.i8.com /pub/1998/8.html (231 words)

	BioMed Central \| Full text \| Production of Se-methylselenocysteine in transgenic plants expressing selenocysteine ... (Site not responding. Last check: 2007-11-07)
		Selenocysteine methyltransferase (SMT), the enzyme responsible for the methylation of selenocysteine to MeSeCys in A.
		This confirmed that reduction of selenate to selenite is a rate-limiting step for Se assimilation into selenocysteine in plants as established previously [48], and explains our observation that SMT over-production does not significantly increase the biosynthesis of MeSeCys in selenate exposed plants.
		The gene encoding selenocysteine methyltransferase (SMT1) was amplified from A.
	www.biomedcentral.com /1471-2229/4/1 (5243 words)

	Selenoxidation by Flavin-Containing Monooxygenases as a Novel Pathway for -Elimination of Selenocysteine Se-Conjugates
		In this study, selenoxidation of selenocysteine Se-conjugates was studied using rat liver microsomes and recombinant human oxidative enzymes.
		For all six selenocysteine Se-conjugates that were tested, it was found that rat liver microsomal incubations led to the formation of pyruvate, whereas the corresponding selenoxides were not observed.
		Inhibition by methimazole and by heat pretreatment and stimulation by n-octylamine indicated that flavin-containing monooxygenases are mainly responsible for pyruvate formation from the selenocysteine Se-conjugates in rat liver microsomes.
	pubs.acs.org /cgi-bin/jtext?crtoec/14/i01/abs/tx0001326 (358 words)

	ipedia.com: Selenocysteine Article (Site not responding. Last check: 2007-11-07)
		Selenocysteine is an amino acid that is present in several enzymes.
		Selenocysteine is an amino acid that is present in several enzymes (for example glutathione peroxidases, tetraiodothyronine 5' deiodinasess, thioredoxin reductases, formate dehydrogenases, glycine reductases and some hydrogenases).
		The specificity of this delivery mechanism is brought about by the presence of an extra protein domain (in bacterial SelB) or an extra subunit (for eukaryotic mSelB) which bind to the corresponding RNA secondary structures formed by the SecIS elements in selenoprotein mRNAs.
	www.ipedia.com /selenocysteine.html (444 words)

	SELB - Selenocysteine-specific elongation factor
		A SECIS-like structure was identified in the 5' non-translated region of the selAB transcript, encoding selenocysteine synthase and SelB.
		The roles of the factors known to be required for Sec incorporation are considered in the context of each step in translation including structural modeling of the differences between the standard elongation factor eEF1A and the Sec-specific counterpart, eEFSec.
		Incorporation of the non-canonical amino acid selenocysteine into proteins requires the activity of the elongation factor SelB which substitutes for the function of EF-Tu in contrast to EF-Tu, SelB binds selenocystylated tRNASec and an mRNA secondary structure adjacent to the UGA selenocysteine codon.
	www.pdg.cnb.uam.es /UniPub/iHOP/gg/101881.html (918 words)

	Targeted insertion of selenocysteine into the alpha subunit of formate dehydrogenase from Methanobacterium formicicum ...
		Selenocysteine incorporation into proteins is directed by an opal (UGA)
		structure were not sufficient for decoding with selenocysteine.
		selenocysteine incorporation, however, was obtained when the loop and the
	jb.asm.org /cgi/content/abstract/174/3/659 (268 words)

	EvolvingCode.net - Selenocysteine (Site not responding. Last check: 2007-11-07)
		Selenocysteine is considered a "non-standard" amino acid because unlike other amino acids, it is not encoded directly by the genetic code.
		Instead, it could be thought of as a "molecular parasite." When seleno-proteins need to be made, the UGA codon (normally a stop codon) is translated as selenocysteine.
		The UGA codon is made to encode selenocysteine by the presence of a SECIS element (SElenoCysteine Insertion Sequence) in the mRNA: "an element lying in the 3'-untranslated region of selenoprotein mRNAs" (1).
	www.evolvingcode.net /index.php?page=Selenocysteine (276 words)

	Selenocysteine (Site not responding. Last check: 2007-11-07)
		Selenocysteine is an amino acid that is present in several enzymes (for example glutathione peroxidases, tetraiodothyronine 5 deiodinasetetraiodothyronine 5' deiodinases, thioredoxin reductases, formate dehydrogenases, glycine reductases and some hydrogenases).
		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.
		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.
	coenzaimq10.com /53656C656E6F6379737465696E65 (567 words)

	Bioactivation of Chemopreventive Selenocysteine Se-Conjugates and Related Amino Acids by Amino Acid Oxidases Novel ...
		Several selenocysteine Se-conjugates have been shown to possess potent chemopreventive activity in animal models for chemical carcinogenesis.
		In the present study, it was investigated whether amino acid oxidases contribute to the bioactivation of selenocysteine Se-conjugates.
		The potential significance of this novel bioactivation route for the chemopreventive activity of selenocysteine Se-conjugates is discussed.
	pubs.acs.org /cgi-bin/jtext?crtoec/14/i08/abs/tx000265r (311 words)

	Cancer Spectrum: Longtin, pp. 504-505.
		The chart above shows that selenocysteine is the 21st amino acid and that it is coded by UGA.
		Others say they do not see the point in revisiting the universal genetic code, even if, as selenocysteine suggests, the power of the paradigm is not 100% accurate.
		regarding whether or not selenocysteine is the 21st amino acid
	jncicancerspectrum.oxfordjournals.org /cgi/content/full/jnci;96/7/504 (1265 words)

	Selenocysteine - Wikpedia (Site not responding. Last check: 2007-11-07)
		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.
		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' untranslated regions of the respective mRNAs.
		In addition, at least one case has been described for an archaeal selenoprotein mRNA containing its SecIS in the 5'-untranslated region.
	www.bostoncoop.net /~tpryor/wiki/index.php?title=Selenocysteine (447 words)

	Qichang Shen - Pediatrics Faculty - UMass Medical School (Site not responding. Last check: 2007-11-07)
		It contains at its active site an unusual amino acid selenocysteine coded by the UGA codon, which is otherwise one of the three translation termination codons.
		We have demonstrated that an sequence element called selenocysteine insertion sequence, located in the 3'- untranslated region of GPx mRNA and postulated to possess a potential stem-loop secondary structure, is not only necessary but also sufficient for signaling the incorporation of selenocysteine into GPx polypeptide chain at the UGA codon.
		Moreover, we are also interested in the applying this unique selenocysteine insertion system to regulation of heterologous gene expression at the translational level, and to site-specific protein labeling with the rare amino acid selenocysteine.
	umassmed.edu /pediatrics/faculty/shen.cfm (253 words)

	Identification and Molecular Cloning of a Human Selenocysteine Insertion Sequence-binding Protein. A BIFUNCTIONAL ROLE ...
		Identification and Molecular Cloning of a Human Selenocysteine Insertion Sequence-binding Protein.
		Prokaryotic and eukaryotic cells incorporate the unusual amino acid selenocysteine at a UGA codon, which conventionally serves
		Secondary structure and stability of the selenocysteine insertion sequences (SECIS) for human thioredoxin reductase and glutathione peroxidase
	www.jbc.org /cgi/content/abstract/273/10/5443 (714 words)

	An RNA-binding protein recognizes a mammalian selenocysteine insertion sequence element required for cotranslational ...
		An RNA-binding protein recognizes a mammalian selenocysteine insertion sequence element required for cotranslational incorporation of selenocysteine -- Lesoon et al.
		In mammalian selenoprotein mRNAs, the recognition of UGA as selenocysteine
		Kinzy, S. A., Caban, K., Copeland, P. Characterization of the SECIS binding protein 2 complex required for the co-translational insertion of selenocysteine in mammals.
	mcb.asm.org /cgi/content/abstract/17/4/1977 (605 words)

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