Enzymes
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Reaction participants Show >> << Hide
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Namehelp_outline
L-seryl-tRNASec
Identifier
RHEA-COMP:9742
Reactive part
help_outline
- Name help_outline 3'-(L-seryl)adenylyl group Identifier CHEBI:78533 Charge -1 Formula C13H17N6O8P SMILEShelp_outline N[C@@H](CO)C(=O)O[C@@H]1[C@@H](COP([O-])(-*)=O)O[C@H]([C@@H]1O)n1cnc2c(N)ncnc12 2D coordinates Mol file for the small molecule Search links Involved in 8 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
- Name help_outline selenophosphate Identifier CHEBI:16144 Charge -3 Formula O3PSe InChIKeyhelp_outline JRPHGDYSKGJTKZ-UHFFFAOYSA-K SMILEShelp_outline [O-]P([O-])([O-])=[Se] 2D coordinates Mol file for the small molecule Search links Involved in 6 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
- Name help_outline H+ Identifier CHEBI:15378 Charge 1 Formula H InChIKeyhelp_outline GPRLSGONYQIRFK-UHFFFAOYSA-N SMILEShelp_outline [H+] 2D coordinates Mol file for the small molecule Search links Involved in 9,521 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
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Namehelp_outline
L-selenocysteinyl-tRNASec
Identifier
RHEA-COMP:9743
Reactive part
help_outline
- Name help_outline 3'-(L-selenocysteinyl)adenylyl group Identifier CHEBI:78573 Charge -1 Formula C13H17N6O7PSe SMILEShelp_outline N[C@@H](C[SeH])C(=O)O[C@H]1[C@@H](O)[C@@H](O[C@@H]1COP([O-])(-*)=O)n1cnc2c(N)ncnc12 2D coordinates Mol file for the small molecule Search links Involved in 2 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
- Name help_outline phosphate Identifier CHEBI:43474 Charge -2 Formula HO4P InChIKeyhelp_outline NBIIXXVUZAFLBC-UHFFFAOYSA-L SMILEShelp_outline OP([O-])([O-])=O 2D coordinates Mol file for the small molecule Search links Involved in 1,002 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
Cross-references
| RHEA:22728 | RHEA:22729 | RHEA:22730 | RHEA:22731 | |
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| Reaction direction help_outline | undefined | left-to-right | right-to-left | bidirectional |
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Publications
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Selenocysteine synthase from Escherichia coli. Analysis of the reaction sequence.
Forchhammer K., Boeck A.
The product of the selA gene, selenocysteine synthase, is a pyridoxal 5-phosphate-containing enzyme which catalyzes the conversion of seryl-tRNA(Sec UCA) into selenocysteyl-tRNA(Sec UCA). Reduction of the aldimine group of pyridoxal 5-phosphate inactivates the enzyme. When reacted with seryl-tRNA( ... >> More
The product of the selA gene, selenocysteine synthase, is a pyridoxal 5-phosphate-containing enzyme which catalyzes the conversion of seryl-tRNA(Sec UCA) into selenocysteyl-tRNA(Sec UCA). Reduction of the aldimine group of pyridoxal 5-phosphate inactivates the enzyme. When reacted with seryl-tRNA(Sec UCA) as sole substrate, pyruvate (and possibly also ammonia) is released; in the presence of a high concentration of potassium borohydride, alanyl-tRNA(Sec UCA) is formed from seryl-tRNA(Sec UCA). These results support the notion that the formyl group of pyridoxal phosphate forms a Schiff base with the alpha-amino group of L-serine with the subsequent 2,3-elimination of a water molecule and the generation of an aminoacrylyl-tRNA(Sec UCA) intermediate. ATP is not required for this reaction step, but it is necessary for the conversion of aminoacrylyl-tRNA into selenocysteyl-tRNA(Sec UCA) which, in addition, requires the SELD protein and reduced selenium. Selenocysteine synthase forms a stable complex with seryl-tRNA(Sec UCA) with one tRNA molecule bound per two 50-kDa monomers. The enzyme does not interact with serine-inserting tRNA species. Taken together, the results show that biosynthesis of selenocysteine takes place in the enzyme-bound state and involves the dehydration of L-serine esterified to tRNA in a first step formally followed by the 2,3-addition of HSe-which is provided by the SELD protein in an ATP-dependent reaction in the form of a reactive selenium donor molecule. << Less
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Structure of selenocysteine synthase from Escherichia coli and location of tRNA in the seryl-tRNA(sec)-enzyme complex.
Engelhardt H., Forchhammer K., Mueller S., Goldie K.N., Boeck A.
Selenocysteine synthase of Escherichia coli catalyses the biosynthesis of selenocysteine in the form of the aminoacyl-tRNA complex, the reaction intermediate being aminoacrylyl-tRNA(sec) covalently bound to the prosthetic group of the enzyme. Selenocysteine synthase and the specific aminoacrylyl-t ... >> More
Selenocysteine synthase of Escherichia coli catalyses the biosynthesis of selenocysteine in the form of the aminoacyl-tRNA complex, the reaction intermediate being aminoacrylyl-tRNA(sec) covalently bound to the prosthetic group of the enzyme. Selenocysteine synthase and the specific aminoacrylyl-tRNA(sec)-enzyme complex as well as the isolated seryl-tRNA(sec) were investigated in the electron microscope and analysed by means of image processing to a resolution of 2 nm in projection. The stoichiometric composition of the selenocysteine synthase molecule was elucidated by scanning transmission electron microscopic mass determination. The enzyme has a fivefold symmetric structure and consists of 10 monomers arranged in two rings. The tRNA is bound near the margin of the dimeric subunits. Principal component analysis of the tRNA-enzyme complexes revealed that the selenocysteine synthase appears to bind only one seryl-tRNA(sec) per dimer, which is consistent with the result of biochemical binding studies. << Less
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Assembly stoichiometry of bacterial selenocysteine synthase and SelC (tRNAsec).
Manzine L.R., Serrao V.H., da Rocha e Lima L.M., de Souza M.M., Bettini J., Portugal R.V., van Heel M., Thiemann O.H.
In bacteria selenocysteyl-tRNA(sec) (SelC) is synthesized by selenocysteine synthase (SelA). Here we show by fluorescence anisotropy binding assays and electron microscopical symmetry analysis that the SelA-tRNA(sec) binding stoichiometry is of one tRNA(sec) molecule per SelA monomer (1:1) rather ... >> More
In bacteria selenocysteyl-tRNA(sec) (SelC) is synthesized by selenocysteine synthase (SelA). Here we show by fluorescence anisotropy binding assays and electron microscopical symmetry analysis that the SelA-tRNA(sec) binding stoichiometry is of one tRNA(sec) molecule per SelA monomer (1:1) rather than the 1:2 value proposed previously. Negative stain transmission electron microscopy revealed a D5 pointgroup symmetry for the SelA-tRNA(sec) assembly both with and without tRNA(sec) bound. Furthermore, SelA can associate forming a supramolecular complex of stacked decamer rings, which does not occur in the presence of tRNA(sec). We discuss the structure-function relationships of these assemblies and their regulatory role in bacterial selenocysteyl-tRNA(sec) synthesis. << Less